United States v. Leeper

22-3110-cr
United States v. Leeper

United States Court of Appeals
for the Second Circuit
_____________________________________

August Term 2024
Argued: February 5, 2025
Decided: August 13, 2026

No. 22-3110
_____________________________________

U
NITED STATES OF AMERICA,

Appellee,

— v. —

K
YLE M. LEEPER,

Defendant-Appellant.
*

_____________________________________

Appeal from the United States District Court
for the Northern District of New York
No. 5:19-cr-0301, David N. Hurd, Judge
_____________________________________

Before: P
ARKER, SULLIVAN, and BIANCO, Circuit Judges.

Defendant-Appellant Kyle Leeper appeals from a judgment entered by the
United States District Court for the Northern District of New York (David N. Hurd,
Judge) on November 29, 2022. Leeper was convicted on his plea of guilty to one

*
The Clerk of Court is respectfully directed to amend the caption as set forth above.

2

count of intentional murder while engaged in a controlled substance offense, in
violation of 21 U.S.C. § 848(e)(1)(A); one count of conspiring to distribute and
possess with intent to distribute methamphetamine, in violation of 21 U.S.C.
§§ 841(a)(1) & (b)(1)(A), 846; and one count of knowingly possessing a firearm and
ammunition after having been convicted of a felony, in violation of 18 U.S.C.
§§ 922(g)(1), 924(a)(2). As part of his plea agreement, Leeper reserved the right to
challenge the district court’s denial of his pretrial motions, including his motions
to suppress evidence seized from his vehicle and evidence obtained by taking a
buccal swab of his DNA.
On appeal, Leeper challenges the denial of those motions, arguing that:
(1) the search warrant affidavit did not establish probable cause to search his DNA
because it did not identify any viable DNA samples with which his DNA could be
compared; (2) the search warrant was invalid because it was issued ex parte even
though there was no reason to proceed ex parte; and (3) the officers’ decision to
hold his vehicle was unreasonable under the Fourth Amendment, rendering the
resulting search unreasonable as well.
For the reasons set forth below, we conclude that: (1) the search warrant
application established probable cause to search Leeper’s DNA; (2) Leeper was not
entitled to notice and an opportunity to be heard prior to the issuance of the search
warrant, and thus the warrant was properly issued ex parte; and (3) the officers’
decision to hold Leeper’s vehicle was reasonable under the Fourth Amendment.
Accordingly, we
AFFIRM the judgment of the district court.
Judge Sullivan concurs in the judgment in a separate opinion.
_____________________________________

B
ENJAMIN SILVERMAN, Law Offices of Benjamin Silverman,
New York, New York, for Defendant-Appellant.
S
TEVEN D. CLYMER, (Thomas R. Sutcliffe, on the brief),
Assistant United States Attorneys, for John A. Sarcone III,
United States Attorney for the Northern District of New
York, for Appellee.

3

JOSEPH F. BIANCO, Circuit Judge:
Defendant-Appellant Kyle Leeper appeals from a judgment of the United
States District Court for the Northern District of New York (David N. Hurd, Judge)
entered on November 29, 2022. Leeper was convicted on his plea of guilty to one
count of intentional murder while engaged in a controlled substance offense, in
violation of 21 U.S.C. § 848(e)(1)(A); one count of conspiring to distribute and
possess with intent to distribute methamphetamine, in violation of 21 U.S.C.
§§ 841(a)(1) & (b)(1)(A), 846; and one count of knowingly possessing a firearm and
ammunition after having been convicted of a felony, in violation of 18 U.S.C.
§§ 922(g)(1), 924(a)(2). As part of his plea agreement, Leeper reserved the right to
challenge the district court’s denial of his pretrial motions, including his motions
to suppress evidence seized from his vehicle and evidence obtained by taking a
buccal swab of his DNA.
On appeal, Leeper challenges the denial of those motions, arguing that:
(1) the search warrant affidavit did not establish probable cause to search his DNA
because it did not identify any viable DNA samples with which his DNA could be
compared; (2) the search warrant was invalid because it was issued ex parte even
though there was no reason to proceed ex parte; and (3) the officers’ decision to
hold his vehicle was unreasonable under the Fourth Amendment, rendering the

4

resulting search unreasonable as well.
For the reasons set forth below, we conclude that: (1) the search warrant
application established probable cause to search Leeper’s DNA; (2) Leeper was not
entitled to notice and an opportunity to be heard prior to the issuance of the search
warrant, and thus the warrant was properly issued ex parte; and (3) the officers’
decision to hold Leeper’s vehicle was reasonable under the Fourth Amendment.
Accordingly, we
AFFIRM the judgment of the district court.
BACKGROUND
1

Leeper was engaged in buying and selling methamphetamine in Indiana,
California, and New York. In early 2019, he traveled to California along with a
housemate, Ramon Nieves Cotto, to purchase methamphetamine. He was
contacted by a woman named Arlene Rodriguez, who offered to help him
purchase drugs. Rodriguez introduced Leeper to Robert Chavez, who arranged
for Leeper to buy three pounds of methamphetamine for $5,000 from his supplier.
Chavez met the supplier and exchanged Leeper’s $5,000 for a backpack, which he
gave to Leeper.

1
The following facts, which are undisputed, are drawn from the Memorandum-Decision
and Order entered by Judge Hurd on December 22, 2021, as well as the Plea Agreement
that Leeper and the government entered into on May 11, 2022.

5

Later that day, Leeper discovered that there was substantially less than three
pounds of methamphetamine in the backpack. In response, Leeper took
Rodriguez hostage at gunpoint and forced her to take him back to Chavez. He
then abducted Chavez, and the group drove around Los Angeles trying to get
more money or drugs to recoup Leeper’s loss. That night, Leeper ordered
Rodriguez to drive to Walmart, where he instructed Cotto to purchase zip ties.
Leeper then bound Chavez’s hands and feet with the zip ties. With a bound
Chavez in tow, Leeper then directed Rodriguez to drive to a deserted area near
Barstow, California, where he removed Chavez from the car, led him away, and
shot him in the back eight times, killing him. Cotto and Rodriguez remained in
the car. Leeper returned to the car alone, and he, Cotto, and Rodriguez drove to
Cortland, New York. Over the course of the trip, Leeper and Rodriguez developed
a romantic relationship, and she continued to assist him with buying and selling
methamphetamine.
On February 19, Leeper and Rodriguez were stopped by officers from the
Cortland County New York Sheriff's Office (“CCSO”) while Leeper was driving a
pickup truck. The officers detained Leeper; held the pickup truck after learning
that neither Leeper nor Rodriguez possessed a valid license and that the vehicle

6

did not have a valid registration; and conducted an inventory search of the truck,
where they found a firearm, ammunition, and four pounds of methamphetamine.
The officers then arrested Leeper and Rodriguez.
Following her arrest, Rodriguez told CCSO officers that Leeper smoked
methamphetamine, that she believed he was selling methamphetamine, and that
she had seen him with both a hand gun and a stun gun. In addition, Rodriguez’s
attorney told CCSO officers that Rodriguez was present during Chavez’s murder
and was willing to speak with the officers about it. A few weeks later, CCSO
officers were contacted by a detective in California who was investigating
Chavez’s homicide.
On April 8, a Cortland County judge issued a warrant to search Leeper’s
person for evidence of second-degree murder, including by collecting his DNA
from a buccal swab. The warrant was issued based on a probable cause affidavit
submitted by Sergeant Garry Williams of the CCSO. Leeper was in custody at the
time. The search warrant identified various pieces of physical evidence found at
the scene of the homicide, including eight .380 caliber fired cartridge casings, seven
.380 caliber projectiles, and cut zip ties.
In 2021, Leeper moved to suppress both the evidence found in his vehicle

7

and evidence derived from the DNA sample. Following an evidentiary hearing,
the district court denied both motions. See generally United States v. Leeper, 577 F.
Supp. 3d 48 (N.D.N.Y. 2021). With respect to the vehicle search, the district court
found that, under the totality of the circumstances, the officers’ decision to tow
Leeper’s truck was reasonable because neither passenger was licensed to drive it,
the truck had no valid registration, and the truck had a severely cracked
windshield, making it unfit for driving. Id. at 63–64. The district court rejected
Leeper’s argument that the decision did not comport with department policy and
was therefore unreasonable, noting that non-compliance with a department policy
is not dispositive of the legality of a search and that “there is uncontradicted
evidence that Wright complied with standard practice even if he had not strictly
followed the written policy.”
2
Id. at 63.
With respect to the DNA sample, the district court found that there was
probable cause for the warrant to issue, given that there was substantial evidence
linking Leeper to Chavez’s murder and “any number of physical instrumentalities

2
Below, Leeper also challenged his temporary detention and the decision to conduct an
inventory search of his vehicle after it was taken into custody. He does not pursue these
arguments on appeal. See Chevron Corp. v. Donziger, 990 F.3d 191, 203 (2d Cir. 2021)
(“Arguments not raised on appeal are deemed abandoned and need not be reviewed by
this Court.”).

8

explicitly tied to Chavez’s murder.”
3
Id. at 72. The district court also rejected
Leeper’s procedural due process challenge to the ex parte warrant proceeding,
stating that “Leeper has failed to point to any support for the notion that the
federal concept of due process would also require an opportunity to be heard
before a search warrant could issue to seize DNA.” Id. Accordingly, the district
court denied Leeper’s suppression motion in its entirety.
Ultimately, Leeper pleaded guilty to three counts: (1) intentional murder
while engaged in a controlled substance offense; (2) conspiring to distribute
methamphetamine; and (3) possessing a firearm knowing that he had previously
been convicted of a felony. However, his plea agreement permitted him to appeal
the district court’s decision to deny his suppression motion as to: “(a) whether
evidence located in and seized from the pickup truck occupied by Kyle M. Leeper
and Arlene N. Rodriguez on February 19, 2019, should have been suppressed
under the Fourth Amendment; and (b) whether a search warrant permitting the
taking of a buccal swab from Kyle M. Leeper on or about April 10, 2019, was
constitutionally invalid because it was issued without a showing of probable cause
and ex parte.” App’x at 221. The plea agreement provided that if Leeper prevails

3
Below, Leeper also argued that the warrant application was supported by insufficiently
reliable evidence. Again, that argument is not raised on appeal.

9

on appeal, “he will be permitted to withdraw his guilty plea without penalty.” Id.
The district court ultimately sentenced Leeper to forty years in prison on both the
murder charge and drug charge and ten years on the firearm charge, all to run
concurrently. This appeal followed.
DISCUSSION
The Fourth Amendment provides that “[t]he right of the people to be secure
in their persons, houses, papers, and effects, against unreasonable searches and
seizures, shall not be violated.” U.S.
CONST. amend. IV. On appeal, Leeper asserts
that the searches of both his DNA and his vehicle violated the Fourth Amendment
and challenges the district court’s denial of his motions to suppress that evidence.
“On an appeal challenging a district court’s ruling on a motion to suppress
evidence, we review its legal conclusions de novo and its findings of fact for clear
error.” United States v. Iverson, 897 F.3d 450, 459 (2d Cir. 2018). “In reviewing the
denial of such a motion, we view the evidence in the light most favorable to the
government.” United States v. Delva, 858 F.3d 135, 148 (2d Cir. 2017) (alteration
adopted) (internal quotation marks and citation omitted). “[W]e may affirm the
denial of the suppression motion on any basis for which there is a record sufficient
to permit conclusions of law, including grounds upon which the district court did

10

not rely.” United States v. Estrada, 430 F.3d 606, 609–10 (2d Cir. 2005).
I. DNA Search
As part of their investigation, CCSO officers obtained a warrant to search
Leeper’s person for evidence of second-degree murder, including by taking a
buccal swab of his DNA. Leeper challenges the validity of the DNA search on two
grounds. The first is substantive: Leeper argues that the warrant application failed
to establish probable cause that his DNA was likely to contain evidence of a crime
because it did not identify any relevant DNA samples with which Leeper’s DNA
could be compared. The second is procedural: Leeper argues that he was denied
procedural due process because the officers obtained a warrant to take a sample of
his DNA without providing him notice or an opportunity to be heard. We address
each of these issues in turn.
a. Probable Cause
In evaluating probable cause, a judge must “make a practical,
common-sense decision whether, given all the circumstances set forth in the
affidavit before him, . . . there is a fair probability that contraband or evidence of a
crime will be found in a particular place.” Illinois v. Gates, 462 U.S. 213, 238 (1983).
“Due to this subjective standard, a reviewing court generally accords substantial

11

deference to the finding of an issuing judicial officer that probable cause exists,
limiting our inquiry to whether the officer had a substantial basis for his
determination.” United States v. Raymonda, 780 F.3d 105, 113 (2d Cir. 2015) (internal
quotation marks and citation omitted); see also Gates, 462 U.S. at 236 (“A
magistrate’s determination of probable cause should be paid great deference by
reviewing courts.”) (internal quotation marks and citation omitted). “Reasonable
minds frequently may differ on the question whether a particular affidavit
establishes probable cause.” United States v. Leon, 468 U.S. 897, 914 (1984).
Accordingly, the Supreme Court has “repeatedly said that after-the-fact scrutiny
by courts of the sufficiency of an affidavit should not take the form of de novo
review.” Gates, 462 U.S. at 236.
Leeper argues that there was no probable cause to search his DNA because
the officers did not establish that there were any DNA samples with which to
compare his DNA. His DNA alone, he argues, is useless; unless the officers
established that there were usable DNA samples collected at the scene or in other
relevant locations with which Leeper’s DNA could be compared, there was no fair

12

probability that evidence of a crime would be found in his DNA on its own.
4

While the parties point us to conflicting lower court authority,
5
this

4
As a threshold matter, the government’s argument that Leeper failed to challenge the
search warrant on these grounds below and therefore review in this court should be for
plain error is without merit. While Leeper’s pretrial motion below made the factually
inaccurate argument that “there are no evidentiary items connected to the murder that
are identified,” it also argued that “flowing from that is the fact that no evidentiary items
have been swabbed for DNA such that a comparison would be possible.” Gov’t App’x
at 30. Accordingly, we consider whether, on de novo review, the district court erred in
concluding that the search warrant for Leeper’s DNA was supported by probable cause.
5
Compare, e.g., United States v. Marshall, No. 11-CR-00381, 2012 WL 2994020, at *3
(W.D.N.Y. July 20, 2012) (“Without evidence that the DNA samples recovered from the
firearms are of a sufficient quality to be used for comparison purposes with the DNA the
government seeks to obtain from the defendants, there is nothing to suggest that
compelling defendants’ DNA will lead to probative evidence in this case.”); United States
v. Pakala, 329 F. Supp. 2d 178, 181 (D. Mass. 2004) (holding, on a motion for an order to
compel, that individuals should not “be subject to even the minimal intrusion of a swab
DNA test unless it is first determined that any substance found on the firearm(s) has
yielded a sufficient DNA profile for comparison”); United States v. Robinson, No. 11-CR-
0325, 2011 WL 7563020, at *3 (D. Minn. Dec. 2, 2011) (finding no probable cause for taking
a DNA sample where “the Government has provided no evidence that it has as yet even
tested the firearm at issue in this case to see whether there is any retrievable DNA
evidence to which any comparison of the DNA sample seized from Defendant can be
made,” because “the Fourth Amendment forbids intrusions on the mere chance that
desired evidence might be obtained”) (internal quotation marks and citation omitted);
United States v. Jennings, No. 21-cr-60193, 2021 WL 5235292, at *8 (S.D. Fla. Nov. 10, 2021)
(“[B]ecause the DNA sample from the firearm had not yet been analyzed, there was no
probable cause to believe that the DNA from Defendant would yield relevant evidence.”);
with, e.g., United States v. Harrison, 683 F. Supp. 3d 184, 205 (N.D.N.Y. 2023) (Hurd, J.)
(“The fact that other magistrates in other judicial districts might have wanted to see a bit
more from the search warrant affiant before signing off on a warrant does not vitiate the
probable cause determination made in this case.”); United States v. Sedillo, 297 F. Supp. 3d
1155, 1181 (D.N.M. 2017) (“[T]he Fourth Amendment does not require the United States
to confirm that evidence collected—in this case, the clothing—will yield a viable DNA
sample before swabbing the arrestees for DNA,” because “[p]robable cause is not a

13

question—whether a search warrant application can establish probable cause
without identifying usable DNA samples taken from physical evidence linked to
the alleged crime—is one of first impression for federal appellate courts. Leeper
asks us to resolve it conclusively by adopting a bright line rule that “[a]bsent any
comparison DNA, there is no way to establish probable cause that a suspect’s DNA
will be evidence of anything.” Appellant’s Br. at 23. But “[p]robable cause is a
fluid concept turning on the assessment of probabilities in particular factual
contexts, and as such is not readily, or even usefully, reduced to a neat set of legal
rules.” Raymonda, 780 F.3d at 113 (internal quotation marks and citations omitted).
We conclude that demonstrating probable cause to obtain a DNA sample
will not always require the government to identify specific DNA samples for
comparison. Nor will it never require such identification. The probable cause
determination in these cases depends on any number of factors, including whether
there is physical evidence that could link a particular suspect to a crime, how much

granular inquiry.”); United States v. Burkhalter, No. 4:18-CR-00036-1, 2023 WL 2653388, at
*5 (W.D. Miss. Mar. 27, 2023) (noting that “courts appear to be split on the issue” and
finding “the reasoning set forth in United States v. Sedillo . . . persuasive”); In re Search
Warrant, No. 24-MJ-02376, 2024 WL 1174726, at *7 (S.D. Fla. Mar. 18, 2024) (finding it
sufficient that there was “probable cause to believe that [the defendant] possessed (and
then tossed) the firearm, and that he may have deposited usable DNA on the firearm,
ammunition, and holster”) (emphasis added).

14

physical evidence there is, the type of physical evidence, and the like.
Here, there was probable cause to search Leeper’s DNA. The search warrant
application identified eight shell casings, seven projectiles, and multiple cut zip
ties recovered at the scene of Chavez’s homicide, as well as the rental car and
Chavez’s body itself, any or all of which could have contained usable DNA
samples against which to test Leeper’s DNA. Indeed, Leeper acknowledges that
the government’s contention that “Leeper would have had ‘ample opportunity to
deposit touch DNA’ . . . is true.” Appellant’s Reply Br. at 18. The supporting
affidavit does not establish with certainty that there would be a sample against
which to compare Leeper’s DNA, but that is not what the Fourth Amendment
requires. “While probable cause requires more than a ‘mere suspicion,’ of
wrongdoing, its focus is on ‘probabilities,’ not ‘hard certainties.’” Walczyk v. Rio,
496 F.3d 139, 156 (2d Cir. 2007) (internal citations omitted). Probable cause
“requires only such facts as make wrongdoing or discovery of evidence thereof
probable.” Id. at 157. The issuing court had a substantial basis for its determination
that the plethora of physical evidence recovered from the scene made it probable
that obtaining a DNA sample from Leeper would lead to the discovery of evidence
of a crime. Accordingly, we conclude that the district court properly denied

15

Leeper’s motion to suppress on this basis.
b. Procedural Due Process
Leeper also challenges the warrant on a procedural ground: that he was
denied procedural due process because the officers obtained an ex parte warrant to
take a sample of his DNA, using a buccal swab, without providing him advance
notice or an opportunity to be heard. “With respect to a claimed due process
violation, we review the district court’s factual determinations for clear error,
while the constitutional significance of those findings, including the ultimate
determination of whether due process has been violated, is reviewed de novo.”
United States v. Epskamp, 832 F.3d 154, 160 (2d Cir. 2016) (alteration adopted)
(internal quotation marks and citation omitted).
Leeper broadly argues that the uniquely revealing nature of DNA implicates
core privacy interests, necessitating a pre-deprivation hearing. Moreover, Leeper
asserts that, “had [he] been afforded notice and a chance to be heard, it is unlikely
that the judge would have issued the search warrant for his DNA because it would
have realized, through an adversarial proceeding, that Sergeant Williams’
supporting affidavit failed to state probable cause that the DNA would yield
evidence of a crime.” Appellant’s Br. at 28–29.

16

In advancing this argument, Leeper principally relies on Mathews v. Eldridge,
424 U.S. 319 (1976), which directs courts, in determining whether procedural
requirements related to the deprivation of property or liberty interests are
constitutionally sufficient, to apply a three-part balancing test that weighs the
following factors:
First, the private interest that will be affected by the official action;
second, the risk of an erroneous deprivation of such interest through
the procedures used, and the probable value, if any, of additional or
substitute procedural safeguards; and finally, the Government’s
interest, including the function involved and the fiscal and
administrative burdens that the additional or substitute procedural
requirement would entail.
Id. at 335.
As an initial matter, the government argues that Mathews has no application
to Fourth Amendment challenges. Leeper counters that the Mathews “test is
applied to myriad cases that require balancing public and private interests in
determining whether sufficient process was granted.” Appellant’s Reply Br. at 3.
To be sure, in the criminal context, we have applied the Mathews test in
determining that a defendant found guilty after trial could not be detained
pending appeal based on an ex parte showing by the government. See United States
v. Abuhamra, 389 F.3d 309, 318, 332 (2d Cir. 2004). Furthermore, we have applied
the Mathews test in addressing the process that was required before a prosecutor

17

could retain a vehicle as potential evidence pending a criminal proceeding. See
Krimstock v. Kelly, 464 F.3d 246, 253–55 (2d Cir. 2006) (applying Mathews and
concluding that “no full-dress adversarial hearing is required to review a
prosecutor’s unilateral determination that a vehicle is needed as potential
evidence” and “district attorneys must be permitted to seek retention orders ex
parte so that defendants cannot use the hearings for discovery or to restrict the
prosecution’s theories at trial”).
Notwithstanding the application of Mathews to examine certain detention
and seizure issues in criminal proceedings, search warrants are different, from
both a historical and practical standpoint, and the government correctly notes that
“no federal appellate court has held that judicial review of search warrant
applications must comport with the Mathews procedural due process framework
or otherwise has suggested that Mathews plays a role in this context.” Appellee’s
Br. at 52. Indeed, without any reference to Mathews, the Supreme Court
unequivocally held over five decades ago that, when a law enforcement officer
applies for a search warrant, the proceeding “is necessarily ex parte, since the
subject of the search cannot be tipped off to the application for a warrant lest he

18

destroy or remove evidence.”
6
Franks v. Delaware, 438 U.S. 154, 169 (1978); United
States v. U.S. Dist. Ct. for E. Dist. of Mich., S. Div., 407 U.S. 297, 321 (1972) (“[A]
warrant application involves no public or adversary proceedings: it is an ex parte
request before a magistrate or judge.”); see also Times Mirror Co. v. United States, 873
F.2d 1210, 1213–14 (9th Cir. 1989) (“[O]ur review of the history of the warrant process
in this country indicates that the issuance of search warrants has traditionally been
carried out in secret. Normally a search warrant is issued after an ex parte
application by the government and an in camera consideration by a judge or
magistrate.”). Thus, we have serious doubts as to whether the Mathews test should
be applied at all to potentially impose additional procedural rules beyond what is
required under the Fourth Amendment. See Gerstein v. Pugh, 420 U.S. 103, 125 n.27
(1975) (“The Fourth Amendment was tailored explicitly for the criminal justice
system, and its balance between individual and public interests always has been
thought to define the ‘process that is due’ for seizures of person or property in
criminal cases, including the detention of suspects pending trial.”); see also

6
In Winston v. Lee, 470 U.S. 753 (1985), the Supreme Court left open the question of
whether “special procedural protections” are warranted under the Fourth Amendment
when the search involves “[a] compelled surgical intrusion into an individual’s body for
evidence,” such as an order for a suspect to undergo surgery to remove a bullet lodged
in his body. Id. at 759, 763 n. 6. No such surgical intrusion is at issue in this case, which
involves only the use of a buccal swab.

19

Abuhamra, 389 F.3d at 328 (rejecting the “view that ex parte submissions at bail
hearings are analogous to ex parte submissions in support of arrest and search
warrants, or wire-tap authorizations” and noting that “[t]he competing interests
at stake in connection with the issuance of warrant and wire-tap authorizations
confer no pre-issuance right to an adversarial hearing on any person”).
However, we need not resolve that issue here because we hold that, even
assuming arguendo that Mathews applies to ex parte warrants for DNA collection
with a buccal swab, the three-part test does not require the government to give
notice and an opportunity to be heard because the government’s compelling law
enforcement interests in being able to obtain ex parte warrants for DNA collection
outweigh an individual’s private interests and the risk of erroneous deprivation in
the absence of that procedure.
7
We address each of the Mathews factors below.

7
We note that New York state courts have recognized a due process right to notice and
an opportunity to be heard when law enforcement seeks a search warrant for an
uncharged suspect’s DNA in non-exigent circumstances. See, e.g., People v. Fomby, 103
A.D.3d 28, 29–30 (N.Y. App. Div. 2012) (citing Matter of Abe A., 437 N.E.2d 265 (N.Y. 1982),
which concerned a search warrant for an uncharged suspect’s blood sample). However,
the New York Court of Appeals has clarified that the suspect’s right to be heard is limited
to “the nature of the bodily intrusion to be authorized by, and the evidence to be collected
under, the warrant,” and he is not entitled to challenge the probable cause showing in the
warrant application, which is what Leeper seeks here. People v. Goldman, 159 N.E.3d 772,
781 (N.Y. 2020); id. (“The constitutional role of the neutral magistrate to determine
whether the warrant application set forth probable cause of defendant’s commission of
the crime and the factual basis for the DNA comparative evidence set forth in the warrant

20

i. The Government’s Interest
As our holding rests on the conclusion that the government has overriding
interests in being able to conduct ex parte warrant proceedings for DNA collection
in the context of an ongoing criminal investigation, we begin with this step of the
Mathews test.
It is beyond dispute that the collection and analysis of DNA are critical tools
used by the government to accurately identify individuals responsible for criminal
conduct, and the government has a “compelling interest in finding, convicting,
and punishing those who violate the law.” Moran v. Burbine, 475 U.S. 412, 426
(1986); see also Schall v. Martin, 467 U.S. 253, 264 (1984) (“The legitimate and
compelling state interest in protecting the community from crime cannot be

application required no supplemental adversarial process. Thus, the method and
procedures employed in taking the saliva undoubtedly respected relevant Fourth
Amendment standards of reasonableness, and defendant’s claim that the failure to
provide him discovery of the extant probable cause and an adversarial hearing
nonetheless warrants the invocation of the exclusionary rule is without constitutional
basis.”). The court also concluded, because the procedure was constitutionally sufficient,
it was “not necessary to address the People’s arguments that Abe A.’s notice procedure
preceding the issuance of a search warrant is no longer required for the minimal intrusion
occasioned by a buccal swab or that the notice procedure does not apply to a suspect who
is in custody.” Id. In any event, federal law, not state law, applies to this federal criminal
prosecution. See United States v. Pforzheimer, 826 F.2d 200, 204 (2d Cir. 1987) (“[W]e are
persuaded that federal law should apply to this federal criminal prosecution, even
though the underlying investigation leading to prosecution was conducted solely by state
officials.”).

21

doubted.”) (internal quotation marks and citation omitted); Nicholas v. Goord, 430
F.3d 652, 669 (2d Cir. 2005) (“There can be little doubt that New York has a strong
government interest in obtaining identifying information from convicted
offenders [through DNA collection] and keeping a record of such information [in
a DNA database].”).
That compelling interest in accurate investigations and prosecutions
obviously includes using DNA analysis to exonerate the innocent. See, e.g., United
States v. Sczubelek, 402 F.3d 175, 185 (3d Cir. 2005) (emphasizing that “DNA samples
will help to exculpate individuals who are serving sentences of imprisonment for
crimes they did not commit and will help to eliminate individuals from suspect
lists when crimes occur”); see also Kaemmerling v. Lappin, 553 F.3d 669, 680 (D.C.
Cir. 2008) (recognizing, in the context of a challenge to the collection and retention
of DNA in a database, that there is a “compelling governmental interest in
accurately and expeditiously solving past and future crimes in order to protect the
public and ensure conviction of the guilty and exoneration of the innocent”).
Often the government cannot advance these compelling interests without
obtaining a search warrant to collect the DNA sample that is necessary for
comparison purposes.

22

The rationale for the longstanding rule that the government should be able
to submit search warrant applications ex parte is also quite obvious: if notice and
an opportunity to be heard were required prior to a search warrant being issued,
the criminal investigation could be compromised in numerous ways including,
inter alia, by the destruction of evidence or other efforts to obstruct justice, as well
as by one or more targets of the investigation fleeing from potential prosecution.
See Franks, 438 U.S. at 169 (“The pre-search proceeding is necessarily ex parte, since
the subject of the search warrant cannot be tipped off to the application for a
warrant lest he destroy or remove evidence.”); United States v. Ulbricht, 858 F.3d 71,
107 (2d Cir. 2017) (affirming denial of a request to unseal a document regarding a
grand jury proceeding because “potential co-conspirators might have learned of
the investigation and attempted to intimidate witnesses or destroy evidence”),
overruled on other grounds by Carpenter v. United States, 585 U.S. 296 (2018).
Leeper, although recognizing that “the government has a strong interest in
obtaining DNA evidence,” argues that these compelling reasons for an ex parte
warrant do not apply to the collection of DNA from a suspect because (1) “the DNA
[sought] from the suspect’s body cannot be spoliated, not even if the suspect dies,”
and (2) “the suspect must be informed before the sample is taken from their body,

23

so the warrant cannot be executed while maintaining a confidential investigation.”
Appellant’s Br. at 28.
These arguments miss the mark. Although the suspect’s DNA cannot be
spoliated and the existence of the criminal investigation is necessarily exposed to
the suspect by the collection of the DNA, there remains a host of means for the
suspect, as well as any co-conspirators, to impede the investigation. In particular,
Leeper overlooks the critical fact that his proposed right to notice and an
opportunity to be heard before the issuance of the warrant would include
providing a copy of the warrant application to the suspect while the investigation
is still pending, or even at its infancy. That application, which must contain
information sufficient to establish probable cause to authorize the DNA collection,
could provide the suspect (and anyone else to whom that suspect shares that
information) with confidential details about the witnesses and evidence gathered
so far in the investigation, including grand jury material, as well as potentially
shed light on law enforcement’s theory of the case and knowledge of the role of
any co-conspirators. Armed with this roadmap of the scope and status of the
government’s investigation, the suspect (even if in custody), as well as any co-
conspirators in the criminal activity (whether known or unknown to law

24

enforcement), could engage in all types of obstruction of that investigation,
including destroying other non-DNA evidence not yet obtained by law
enforcement and intimidating or tampering with potential witnesses.
Moreover, the suspect (if he is not already in custody) could flee the
jurisdiction once he is given notice of the search warrant application, thereby
thwarting the collection of the DNA from him or any future criminal prosecution.
Even if the suspect is in custody, any non-incarcerated co-conspirators would have
their own opportunity to flee, especially if the warrant application were made
known to them and revealed that the investigation was well-developed and
additional arrests were imminent. See Application of Dow Jones & Co., Inc., 842 F.2d
603, 611 (2d Cir. 1988) (“[T]argets learning of their possible indictment might flee
or tamper with . . . witnesses.”). Indeed, these compelling law enforcement
interests in protecting the confidential details of an ongoing criminal investigation
are precisely why government applications for search warrants typically remain
sealed until after the target is arrested.
Other courts have similarly recognized the compelling government interests
in maintaining the confidentiality of search warrant applications while an
investigation is pending. For example, in Matter of EyeCare Physicians of America,

25

100 F.3d 514 (7th Cir. 1996), companies whose premises were searched pursuant to
warrants filed a motion to have the search warrant applications and affidavits
unsealed to allow them to assess whether to challenge the government’s search.
Id. at 515. In affirming the denial of the motion, the Seventh Circuit noted that
disclosure of the affidavits would breach the secrecy of the grand jury
investigation and outlined other potential adverse ramifications from such a
disclosure:
Additional consequences in disclosing the sealed affidavits include:
the identity of unnamed subjects not yet charged would be revealed;
there may be mistaken notions concerning who might and might not
be cooperating with the government or who may be subjects; there
may be misunderstandings about the parameters of the government’s
investigation; the privacy of the innocent and the implicated would
be threatened; and the cooperation of present and potential witnesses
could be compromised or influenced. . . . We agree with the
magistrate judge and the district court that disclosure of the affidavits
might very likely impair the ongoing criminal investigation.
Id. at 519; see also Media Gen. Operations v. Buchanan, 417 F.3d 424, 429 (4th Cir. 2005)
(holding that there was no right to view the sealing orders for the search warrant
prior to the execution of the warrant and emphasizing that “[a] rule to the contrary
would endanger the lives of officers and agents and allow the subjects of the
investigation to destroy or remove evidence before the execution of the search
warrant”); In re Search Warrant for Secretarial Area Outside Off. of Gunn, 855 F.2d 569,

26

573 (8th Cir. 1988) (“[T]he very objective of the search warrant process, the seizure
of evidence of crime, would be frustrated if conducted openly.”). It is likewise not
hard to imagine how one or more of these adverse consequences to an ongoing
criminal investigation could potentially result from the disclosure of a search
warrant application to collect DNA from a suspect, even when the suspect is in
custody.
In addition to the damage that could arise from disclosure of the details of
the search warrant application, the delay that would inevitably result from pre-
seizure notice and an opportunity to be heard could similarly impede criminal
investigations where time is often of the essence and any delay could jeopardize
public safety. See generally In re Sealed Case, 77 F.4th 815, 828 (D.C. Cir. 2023) (“Time
is of the essence when the government seeks evidence needed in a criminal case,
so there may be little opportunity to fully litigate a substantial constitutional claim
while holding in abeyance the execution of a search warrant.”). Importantly, in
many instances, the delay could be substantial because a suspect may need time
to retain an attorney, the attorney will then need time to prepare a motion to which
the government will need to respond, and the court may be required to hold an
evidentiary hearing. As the Supreme Court has explained, “[t]his Court has

27

recognized, on many occasions, that where a State must act quickly, or where it
would be impractical to provide predeprivation process, postdeprivation process
satisfies the requirements of the Due Process Clause.” Gilbert v. Homar, 520 U.S.
924, 930 (1997) (collecting cases); see also Parratt v. Taylor, 451 U.S. 527, 539 (1981)
(“[E]ither the necessity of quick action by the State or the impracticality of
providing any meaningful predeprivation process, when coupled with the
availability of some meaningful means by which to assess the propriety of the
State’s action at some time after the initial taking, can satisfy the requirements of
procedural due process.”); accord Catanzaro v. Weiden, 188 F.3d 56, 61–63 (2d Cir.
1999). Those are precisely the circumstances present here.
Although Leeper notes that the government sometimes opts to proceed by
way of a court order to extract DNA with notice to the suspect when that suspect
is already in custody, that voluntary decision by the government—in some
circumstances where they have determined that obstruction of justice and flight
are not substantial risks in that particular investigation or prosecution—does not
support the argument that the government should be required to give notice in any
such situation. See Times Mirror Co., 873 F.2d at 1217 (concluding that “the fact that
search warrants and supporting affidavits are often filed with the district court

28

without seal . . . merely describes a practice in cases where the government
presumably believes secrecy is unnecessary” and does not demonstrate that
sealing is never warranted). For example, the government may voluntarily opt to
seek a court order to collect DNA with notice (rather than seek an ex parte search
warrant) when an incarcerated defendant has already been arrested for the crime,
is believed to have acted alone in connection with the crime, and is either already
aware of the details of the investigation from discovery already provided to his
counsel in the criminal case or is not in a position to destroy the evidence or
intimidate the witnesses supporting his current prosecution. Those circumstances
are a far cry from other situations where the risks to the investigation from
disclosure of the warrant application remain high at the time of the DNA
collection, such as where an investigation is far from complete, its details are
unknown, and/or co-conspirators remain at large.
Leeper also suggests that the government should be required, in each
individual situation involving a request to extract a person’s DNA, to demonstrate
that there are sufficient law enforcement reasons to justify an ex parte application.
See Appellant’s Reply Br. at 14 (“[I]f . . . the government has a reason to make the
application ex parte, then it can explain the reasons at that time; but that is not

29

grounds to allow, by default, all requests to extract a person’s DNA to be made ex
parte and without prior notice to them.”). In other words, under Leeper’s
approach, when the government seeks an ex parte search warrant to collect DNA
from a suspect, the government should be required in each case to “present[]
exigent circumstances warranting the postponement of notice and the opportunity
for an adversarial hearing.” United States v. 4492 S. Livonia Rd., 889 F.2d 1258, 1265
(2d Cir. 1989). We disagree.
To be sure, “[t]he determination of whether one is entitled to a pre-
deprivation hearing is fact-specific, as ‘due process is flexible and calls for such
procedural protections as the particular situation demands.’” Ciambriello v. Cnty.
of Nassau, 292 F.3d 307, 319 (2d Cir. 2002) (quoting Mathews, 424 U.S. at 334).
However, for the reasons discussed above, it is clear that requiring the government
to demonstrate exigent circumstances warranting an ex parte search application in
each individual case where DNA collection is sought from a suspect (even if such
a rule is limited to incarcerated suspects) is unworkable and insufficient to protect
the government’s compelling interest in, inter alia, maintaining the confidentiality
of its search warrant application, especially because it is often difficult for the
government to identify and articulate at the time of that application exactly how

30

or where a target or his co-conspirators could undermine the investigation if
provided with the search warrant application. Indeed, law enforcement officers
routinely obtain ex parte search warrants to gather all types of evidence that belong
to (or implicate the privacy interests) of an incarcerated individual, including from
his or her home, car, rental space in a storage facility, computer, cellphone, email
account, or social media accounts. No court has suggested, nor does Leeper even
suggest, that the government should be required to provide sufficient justification
for the ex parte nature of the application in each and every one of those situations
simply because the individual is incarcerated and thereby may not be able to
personally undermine the investigation if he is provided with notice and an
opportunity to be heard before the issuance of the warrant. Instead, in each of
those situations, the compelling law enforcement reasons for maintaining the
secrecy of the investigation and the often unknowable risks of disclosing the
application to the target of the investigation, even when the target is incarcerated,
would be undermined by any such case-by-case requirement. All of those
compelling justifications supporting ex parte warrants in those situations apply
with equal force to a search warrant that seeks the collection of DNA from a
suspect like Leeper, even when he is in custody. In short, under Mathews, the

31

particular demands of the search warrant application process, including the
practical realities and exigencies of ongoing criminal investigations and the
importance of maintaining the confidentiality of search warrant applications
during that investigation, support allowing the government to seek a search
warrant for the collection of a DNA sample from a suspect without providing that
suspect with notice and an opportunity to be heard at the time of the warrant
application.
ii. Leeper’s
Private Interests
With respect to the Mathews factor that considers the private interests
impacted by the government’s action, Leeper argues that DNA is different than
other forms of evidence routinely seized from a target in that he has an
“exceptionally high interest in the privacy of his genetic makeup” as once it is
extracted and “posted on government databases,” “it is forever in the public
sphere.” Appellant’s Br. at 32–33. Leeper further asserts that his DNA sample
could be used to reveal his “medical history, family history, and aspects of [his]
sexual history”—i.e., intimate personal details that should be afforded a high
degree of privacy. Id. at 33. As set forth below, we conclude that these privacy
interests are insufficient to outweigh the government’s compelling justifications

32

for obtaining ex parte warrants to collect DNA evidence.
As a threshold matter, it is important to note that the ex parte warrant in this
case only authorized the collection of DNA via a buccal swab. The Supreme Court
has held that buccal swabs amount to only a “negligible” intrusion on one’s
person. Maryland v. King, 569 U.S. 435, 446 (2013) (describing a buccal swab as a
“gentle process” that “involves but a light touch on the inside of the cheek”).
Indeed, we have noted that, even an intrusion to take a blood sample, “while
subject to the Fourth Amendment, is minimal,” and “where inmates are routinely
subject to medical procedures, including blood draws, and where their expectation
of bodily privacy, while intact, is diminished, the intrusiveness of a blood draw is
even further minimized.” Goord, 430 F.3d at 669 (internal citations omitted).
We recognize that, by testing the saliva sample from the buccal swab, the
government will have access to the suspect’s DNA, which can reveal intimate
details about him. This access to such details, however, does not necessarily lead
to the conclusion that a special constitutional rule is required with respect to the
collection and analysis of that type of evidence in a criminal investigation. For
example, in the context of a Fourth Amendment analysis, numerous courts have
held that, if law enforcement obtains an individual’s saliva (or some other bodily

33

material) that has been abandoned in a public place, no search warrant is required
before the DNA from that sample can be analyzed—notwithstanding the intimate
details that could be revealed from it. See, e.g., Emerson v. Kelly, No. 1:14-cv-00809,
2015 WL 3968250, at *14 (N.D. Ohio June 30, 2015) (“[A] person has no reasonable
expectation of privacy in his or her DNA profile extracted from a lawfully obtained
DNA sample.”) (internal quotation marks and citation omitted); United States v.
Scott, No. 10-00027-01-CR, 2011 WL 5387601, at *6 (W.D. Mo. Oct. 3, 2011) (“[T]he
DNA obtained from the cup Defendant left on the coffee table should not be
suppressed as the warrantless search of abandoned property does not violate the
Fourth Amendment.”); see also United States v. Hicks, No. 2:18-cr -20406, 2020 WL
7704556, at *4 (W.D. Tenn. May 27, 2020) (noting that “[o]ther courts have found
one’s abandonment of an item containing his or her DNA sufficient to permit the
government to conduct forensic analysis on that sample without a warrant”)
(collecting cases). In any event, for due process purposes, we conclude that any
additional privacy interests that a suspect in a criminal investigation has in the
DNA material of a sample lawfully obtained pursuant to a search warrant do not
sufficiently outweigh the compelling justifications that exist, as discussed supra,
for not requiring law enforcement to give that suspect notice and an opportunity

34

to be heard in connection with the search warrant application for that sample.
Although Leeper suggests that his proposed exception to the general rule
that ex parte search warrants are permitted would be a narrow one because of the
unique nature of DNA and the personal details revealed by its examination, we
have our doubts about the narrowness of the rule he proposes. Indeed, if the
ability of a search warrant to reveal intimate details of a person’s life were
sufficient under the Due Process Clause to prompt a requirement of notice and an
opportunity to be heard at the time of the search warrant application, then many
types of search warrants would undoubtedly fall within that rule. For instance, in
Riley v. California, 573 U.S. 373 (2014), the Supreme Court emphasized that
cellphones are functionally “a digital record of nearly every aspect of [a person’s]
li[fe]—from the mundane to the intimate.” Id. at 395. Cellphones may contain
intimate conversations with loved ones, GPS locations, medical and business files,
and real-time monitoring of health statistics, among other revealing information.
Id. at 394–96, 403. Moreover, since the decision in Riley over ten years ago,
technology has only evolved and the types and volume of information that may

35

be stored on an electronic device has increased exponentially.
8
Thus, electronic
devices may hold just as much “vast and sensitive” information—if not more—
than a DNA analysis. Appellant’s Br. at 31. Yet adopting Leeper’s reasoning
would seemingly prevent law enforcement from proceeding with an ex parte
warrant application to obtain the contents of a cellphone already in police custody
and owned by an incarcerated person. No court has suggested that such a rule
exists with respect to cellphones, and, in our view, Leeper’s reasoning would
fundamentally change the warrant application process for many types of searches,
particularly for suspects who are incarcerated, and run the risk of severely
impeding law enforcement across a broad spectrum of investigations.
Finally, with respect to his private interests, Leeper points out that the
invasion of privacy is magnified with respect to the collection of DNA because it
is maintained in a public database. We have acknowledged, in connection with
the extraction and analysis of convicted felons’ blood for DNA-indexing purposes
pursuant to a statute, that DNA collections constitute multi-tiered “intrusions” on
the subject of the collection—a first “physical intrusion” occurs when the DNA

8
For example, there are now applications available that allow a person to upload and
analyze their DNA data to their cellphone, which would likewise be available to law
enforcement during a cellphone search. See What we do, GENOMAPP (last visited March 9,
2026), https://genomapp.com/en/what-we-do/ [https://perma.cc/R5GL-YZSJ].

36

sample is actually taken, and a second occurs during the “analysis and
maintenance of [the] DNA information,” which we have explained is a
“potentially a far greater intrusion than the initial extraction,” since the obtaining
entity may “maintain[] DNA records indefinitely.” Goord, 430 F.3d at 669–70
(upholding New York’s DNA database statute against a Fourth Amendment
challenge).
Here, although we likewise recognize the privacy concerns implicated by
the ability of law enforcement to maintain the DNA permanently in a national
database, Leeper overlooks the substantial safeguards that exist with respect to
those concerns. As a threshold matter, contrary to Leeper’s suggestion, the
collection of a DNA sample does not necessarily lead to nationwide publication of
that sample in the database. As the government correctly points out, it is only after
a conviction that maintenance on the national index would be required. See 34
U.S.C. § 40702(a)(1)–(2); see generally United States v. Amerson, 483 F.3d 73, 86 (2d
Cir. 2007) (explaining that, once a defendant is convicted, the “expectation of
privacy in his or her identity is severely diminished”). Furthermore, there are
numerous safeguards governing the use and maintenance of DNA information
within the national index. For example, DNA information may only be disclosed

37

in limited circumstances and to a limited number of actors: (1) to criminal justice
agencies for law enforcement purposes; (2) in judicial proceedings; (3) for criminal
defense purposes; and (4) for population statistics databases and research, only if
personally identifiable information is removed. 34 U.S.C. § 125 92(b)(3). Consistent
with these protections, if the subject of a DNA analysis is exonerated, acquitted, or
the charges are dropped, DNA information may be expunged from the database.
34 U.S.C. § 12592(d)(1)–(2). Accordingly, it is not the case, as Leeper argues, that
once DNA is collected, pursuant to an ex parte warrant or otherwise, that a
suspect’s DNA “is forever in the public sphere” without any safeguards.
9

Appellant’s Br. at 33; see Goord, 430 F.3d at 671 (“Given the limits imposed on the
collection, analysis, and use of DNA information by the statute, . . . the intrusion

9
The ex parte warrant for Leeper’s DNA collection was issued by a state judge in Cortland
County, New York. That the warrant originated in the state judicial system does not
impact our analysis with respect to these procedural safeguards. In Goldman, the New
York Court of Appeals emphasized that “[New York law] demands an accredited state
laboratory conform to the national DNA index system in developing the DNA profile
from limited loci and imposes a similar duty to maintain confidentiality of the results of
DNA testing to avoid unwarranted disclosures.” 159 N.E.3d at 780 (citing, inter alia, New
York Executive Law §§ 995-c, 995-d). Indeed, the court concluded, “[a]ssuming the
applicability of those significant statutory safeguards, there is no need for an adversarial
hearing to determine whether the collection of a DNA sample amounts to an
unreasonable invasion of privacy in a particular case.” Id. Moreover, when DNA
information collected by a state or local criminal justice agency is included in the national
index, the federal restrictions regarding use and disclosure apply. See 34 U.S.C.
§ 12592(b)(3).

38

on privacy effected by the statute . . . is insufficient to outweigh the state’s strong
interest in maintaining a DNA index.”); Roe v. Marcotte, 193 F.3d 72, 80 (2d Cir.
1999) (finding sufficient safeguards in a DNA statute that “restricts access to and
secures the confidentiality of the results and provides for the expungement of the
results from the data bank upon the reversal or dismissal of a conviction”) (internal
citations omitted).
In sum, under the Mathews test, we conclude that Leeper’s private interests
in his DNA do not outweigh the government’s compelling interests in conducting
effective law enforcement investigations that are aided by the ability to obtain ex
parte search warrants for DNA collection from a suspect, even when that suspect
is incarcerated.
iii. Risk of Erroneous Deprivation
Finally, we examine the Mathews factor that addresses the risk of erroneous
deprivation—i.e., the likelihood that holding pre-deprivation hearings prior to the
issuance of DNA warrants would reduce the chance of erroneous outcomes. See
Mathews, 424 U.S. at 335. As set forth below, we conclude that this factor does not
support a requirement of notice and an opportunity to be heard before a search
warrant for DNA collection is considered.

39

Importantly, even in the absence of any ability by a suspect to challenge the
issuance of a search warrant, the Fourth Amendment guards against unreasonable
searches and seizures by requiring the government to demonstrate probable cause
to a judicial officer before the warrant can be issued. U.S.
CONST. amend. IV. The
Supreme Court has explained that the “long-prevailing constitutional standards
of probable cause embod[y] the best compromise that has been found for
accommodating the often-opposing interests in safeguarding citizens from rash
and unreasonable interferences with privacy and in seeking to give fair leeway for
enforcing the law in the community’s protection.” Dunaway v. New York, 442 U.S.
200, 208 (1979) (alterations adopted) (internal quotation marks and citation
omitted). Thus, “an ex parte probable cause determination before a judicial officer
reduces the possibility of an erroneous deprivation.” 4492 S. Livonia Rd., 889 F.2d
at 1265.
Moreover, the risk of erroneous deprivation is further minimized by the
exclusionary rule, which functions to “deter future Fourth Amendment
violations.” Davis v. United States, 564 U.S. 229, 248 (2011); see also Abuhamra, 389
F.3d at 328 (distinguishing ex parte submissions at bail hearings from ex parte
submissions in support of warrants and wire-tap applications because “[o]nce

40

such orders are executed . . . the ex parte submissions are generally unsealed—in
the case of the arrest and search warrants, usually immediately—and parties
whose liberty or property interests are affected are afforded opportunities to
challenge the legality of the actions”); United States v. Smith, 575 F. Supp. 3d 542,
555 (E.D. Pa. 2021) (holding that, because the police obtained the defendant’s DNA
sample in violation of the Fourth Amendment, “the exclusionary rule compel[led]
the suppression of any evidence of Defendant’s DNA sample and the forensic
analyses derived from it as the tainted fruit of unlawful government conduct”)
(internal quotation marks and citation omitted). Here, following his indictment in
federal court, Leeper had the opportunity to challenge the probable cause
determination for the issuance of the warrant which, as discussed supra, the district
court correctly rejected.
These safeguards are sufficient under these circumstances to protect a
suspect who is the subject of DNA collection pursuant to an ex parte search warrant
from a violation of his Fourth Amendment rights in connection with the issuance
of the warrant or an erroneous outcome in his criminal proceeding. See generally
United States v. Grubbs, 547 U.S. 90, 99 (2006) (“The Constitution protects property
owners not by giving them license to engage the police in a debate over the basis

41

for the warrant, but by interposing, ex ante, the deliberate, impartial judgment of a
judicial officer . . . between the citizen and the police, and by providing, ex post, a
right to suppress evidence improperly obtained and a cause of action for
damages.”) (internal quotation marks and citation omitted).
Leeper again argues that a different rule is required in the context of DNA
collection because the deprivation resulting from any unconstitutional action by
law enforcement is more damaging when DNA is collected, as compared to other
types of searches. We are unpersuaded. Neither the Supreme Court nor any other
circuit court has ever suggested that the ex parte process for obtaining of search
warrants should be abandoned because the searches may involve substantial
bodily intrusions, such as body cavity searches, see, e.g., Sloley v. VanBramer, 945
F.3d 30, 40 (2d Cir. 2019), or the collection of evidence from an individual’s
residence, United States v. Sandalo, 70 F.4th 77, 79 (2d Cir. 2023), or a cellphone,
Riley, 573 U.S. at 403, and we can discern no reason to depart from that process
where the search involves the collection of a DNA sample with a buccal swab for
the purposes of DNA analysis in a criminal investigation.

* * *
In sum, under the Mathews test, we conclude that the government’s

42

compelling interests in the confidentiality of the search warrant application for the
collection of a suspect’s DNA sample during an ongoing investigation are
sufficiently strong—even when the suspect is incarcerated—to outweigh the
private interests implicated by that search. Moreover, the existing procedural
safeguards for an ex parte application, as well as the ability of the suspect in any
subsequent criminal proceeding to challenge any evidence seized pursuant to the
warrant, are sufficient to guard against the risk of erroneous deprivation.
Therefore, even assuming arguendo that the Mathews test applies to ex parte search
warrants for the collection of a DNA sample from a suspect via a buccal swab, the
government is not required under Mathews to provide notice and an opportunity
to be heard in connection with that warrant application, whether or not that
suspect is already in custody. Accordingly, the lack of notice to Leeper in
connection with his search warrant was not a constitutional violation, and it
provides no basis to disturb his conviction.
II. Vehicle Inventory Search
Finally, Leeper challenges the hold and related search of his vehicle, arguing
that the fruits of this search should be suppressed. Leeper’s challenge fails because
the officers’ decision to hold his car did not violate the Fourth Amendment.

43

When considering similar questions, “[s]ome courts have concluded that
there are two inquiries: first, whether the impoundment of a car is reasonable; and
second, if so, whether the subsequent search of the car after the impoundment is
reasonable.” United States v. Lyle, 919 F.3d 716, 730 n.2 (2d Cir. 2019). This case
involves only the former question. Leeper does not challenge the CCSO policy
requiring an inventory search for vehicles that are properly impounded or held,
nor does he challenge the decision to search the vehicle itself as unreasonable.
Leeper argues only that the decision to hold his truck, which in turn triggered the
search, was unreasonable and pretextual—not that conducting an inventory
search was independently unreasonable once that decision had been made. As in
Lyle, where the defendant “challenged only the impoundment and not the
subsequent search of the rental vehicle,” we “need not reach the second inquiry.”
Id.
Turning then to the question whether the officers’ decision to hold Leeper’s
vehicle was reasonable, we start with the well-established notion “that police have
the authority, despite the absence of a warrant, to seize and remove from the
streets automobiles in the interests of public safety and as part of their community
caretaking functions—an authority that is beyond reasonable challenge.” Id. at

44

728. “[U]nder this community caretaking exception to the warrant requirement,
police officers may exercise their discretion in deciding whether to impound a
vehicle, so long as that discretion is exercised according to standard criteria and
on the basis of something other than suspicion of evidence of criminal activity.”
Id. (internal quotation marks and citation omitted).
We have consistently held that officers’ decisions to seize and remove
vehicles were reasonable in circumstances where, due to arrests, suspended
licenses, or other reasons, no driver would be available to remove the vehicle from
its location. In Lyle, where the car’s driver and sole occupant had a suspended
license, this Court reasoned that “by impounding the vehicle, the officer ensured
that the rental vehicle was not left on a public street in a busy midtown Manhattan
location where it could have become a nuisance or been stolen or damaged and
could have become illegally parked the next day.” Id. at 731. The same was true
in United States v. Lopez, where “the circumstances called for the impoundment of
[Lopez’s] car, as Lopez was arrested for driving it while intoxicated.” 547 F.3d 364,
372 (2d Cir. 2008).
The same reasoning applies here. As the district court found, Leeper’s
vehicle had an expired registration, such that no one could lawfully drive it away;

45

even if someone could, neither Leeper nor Rodriguez had a valid license. In these
circumstances, the officers’ decision to hold the truck was reasonable.
Leeper’s arguments to the contrary are unpersuasive. First, Leeper argues
that the decision to impound his vehicle was unreasonable because the CCSO
officers did not adhere to their standardized written procedures. This is neither
true nor dispositive. The district court found that “there is uncontradicted
evidence that Wright complied with standard policy.” App’x at 184. Although
Leeper urges a different interpretation of the policy, he provides no reason to
disturb the district court’s finding, which was supported by Officer Wright’s
testimony about the policy. And regardless, “[w]hile the existence of and an
officer’s adherence to a standardized criteria may be helpful in evaluating the
reasonableness of an impoundment, we decline to adopt a standardized
impoundment procedure requirement.” Lyle, 919 F.3d at 731.
Next, Leeper seeks to distinguish this case from Lyle and Lopez, noting the
undisputed fact that his truck was parked in a commercial parking lot—not on a
public street, as in Lyle and Lopez. That is true, but again it is not dispositive. Our
inquiry does not turn on any one individual fact; “the touchstone of the Fourth
Amendment is reasonableness, which, in turn, is measured in objective terms by

46

examining the totality of the circumstances.” Id. (internal quotation marks and
citation omitted). Here, as noted above, no one on the scene could lawfully drive
the vehicle away from its location. Although it was in a private parking lot, Leeper
had not sought permission to leave the truck there, there was no telling how long
it would remain there, and it was certainly reasonable to conclude it might have
“become a nuisance or been stolen or damaged.” Id.
Last, Leeper claims the decision to impound the truck was pretextual and
was simply an excuse to search it. But the sole basis for that claim is Leeper’s ipse
dixit that there was no community caretaking reason to impound the truck, which
we have already rejected.
In sum, we hold that the officers’ decision to hold the truck, which had
neither a valid registration nor any driver who could remove it legally, was
reasonable under the Fourth Amendment, and the fruits of the accompanying
search need not be suppressed.
CONCLUSION
For the foregoing reasons, we
AFFIRM the judgment of the district court.

23-3110-cr
United States v. Leeper
RICHARD J. SULLIVAN, Circuit Judge, concurring in the judgment:
Although I agree with the majority’s ultimate outcome, I write separately
because I believe that Mathews v. Eldridge, 424 U.S. 319 (1976), is inapplicable to
search warrants. I would hold as much, without assuming arguendo that Mathews
does apply and then conducting the procedural due-process analysis that it
requires.
It is well established that the standards governing searches and seizures are
derived from the Fourth Amendment. The Supreme Court reached that
conclusion more than fifty years ago. See Gerstein v. Pugh, 420 U.S. 103, 125 n.27
(1975). Holding that the Fourth Amendment is “tailored explicitly for the criminal
justice system,” the Court emphasized that only this Amendment’s “balance
between individual and public interests” could define the “process that is due” for
searches and seizures involving criminal defendants. Id. Indeed, alternate analytic
frameworks developed in the context of civil deprivations – such as Mathews’s
due-process balancing test – are “irrelevant in the wholly different context of the
criminal justice system.” Id. (emphasis added). The reason is simple: the Fourth
Amendment’s original and enduring role is to “safeguard” citizens “from
interferences with privacy and from unfounded charges of crime” while giving

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“fair leeway” to the government to “enforc[e] the law in the community’s
protection.” Brinegar v. United States, 338 U.S. 160, 176 (1949); see also Gerstein, 420
U.S. at 125 n.27 (“The Fourth Amendment probable cause determination is . . . the
first stage of an elaborate system, unique in jurisprudence, designed to safeguard
the rights of those accused of criminal conduct.”). In other words, because the
Fourth Amendment already strikes the proper balance between the public and
private interests at stake in government searches, there is no need for additional
balancing under the Due Process Clause.
In the context of search-warrant applications specifically, the Supreme
Court has affirmed the constitutionality of ex parte proceedings in every case in
which it has considered the question. In United States v. United States District Court
for the Eastern District of Michigan, for example, the Court underscored that a
search-warrant application is an “ex parte request before a magistrate or judge”
involving “no public or adversary proceedings.” 407 U.S. 297, 321 (1972). That
same description appeared in Franks v. Delaware, where the Court reiterated that,
as a general matter, search-warrant proceedings are “necessarily ex parte, since the
subject of the search cannot be tipped off to the application for a warrant lest he
destroy or remove evidence.” 438 U.S. 154, 169 (1978). Together, both cases leave

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no doubt that the requirements of the Fourth Amendment – even when met ex
parte – constitute all the “process that is due” when the government applies for a
search warrant. Gerstein, 420 U.S. at 125 n.27 (internal quotation marks omitted).
Rather than holding that the Fourth Amendment alone governs search-
warrant applications – and that it clearly countenances ex parte proceedings – the
majority’s opinion entertains the idea that Mathews’s procedural due-process
framework could modify or even trump the Fourth Amendment analysis. See Maj.
Op. at 16–17. While admitting that “search warrants are different” and that it has
“serious doubts as to whether the Mathews test should be applied,” the majority
nonetheless decides that it “need not resolve that issue here” because “even
assuming arguendo that Mathews applies to ex parte warrants for DNA collection
with a buccal swab, . . . the government’s compelling law enforcement interests .
. .
outweigh an individual’s private interests.” Id. at 17–18. To justify its decision to
leave that issue for another day, the majority cites two cases that it believes lend
credence to the view that Mathews may apply in search-warrant cases. See id. at
16–17. But neither decision stands for that proposition.
The first, United States v. Abuhamra, distinguishes between (i) proceedings to
determine whether a defendant should be detained pending appeal – a context in

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which we did apply Mathews – and (ii) search-warrant applications, in which we
clarified that there is “no pre-issuance right to an adversarial hearing [for] any
person.” 389 F.3d 309, 328 (2d Cir. 2004). Abuhamra, in other words, reaffirmed the
principle that the Fourth Amendment supplies all the “process that is due” in
applications for search warrants. Gerstein, 420 U.S. at 125 n.27 (internal quotation
marks omitted).
The second case cited by the majority, Krimstock v. Kelly, concerned
prosecutors’ retention of private vehicles as evidence in potential criminal
proceedings against the drivers – though not necessarily the owners – of those
vehicles. 464 F.3d 246, 253 (2d Cir. 2006). Although we did apply Mathews in
Krimstock, we did so only because the case “involve[d] the deprivation of
property” affecting challengers who might be “innocent owner[s] who [were] no[t]
part[ies] to the criminal proceeding[s].” Id. at 254. Noting that it would be
“redundant” and “inconsistent” to apply the “vaguer notion of ‘due process’” to
“criminal proceedings” governed by the Bill of Rights, we explained that Mathews
was relevant exclusively because neither party was challenging “an underlying
criminal proceeding or the procedural rights due [a] criminal defendant.” Id. Put
simply, Krimstock is a deprivation of property case, not a criminal procedure or

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search-warrant case. Where search warrants are involved, there can be no doubt
that the only “process that is due” is supplied by the Fourth Amendment. Gerstein,
420 U.S. at 125 n.27 (internal quotation marks omitted).
In my view, the majority’s willingness to entertain the applicability of
Mathews to search-warrant applications is unjustified – and profoundly unwise.
Both this Court and the Supreme Court have counseled against importing the
Mathews scheme into the procedural framework enshrined in the Bill of Rights.
Indeed, because the “Bill of Rights speaks in explicit terms to many aspects of
criminal procedure,” the “expansion of those constitutional guarantees under the
open-ended rubric of the Due Process Clause invites interference with . . . the
careful balance that the Constitution strikes between liberty and order.” Medina v.
California, 505 U.S. at 443; see also id. (“[I]t has never been thought that decisions
under the Due Process Clause establish this Court as a rule-making organ for the
promulgation of . . . rules of criminal procedure.” (alteration adopted and internal
quotation marks omitted)); Hines v. Miller, 318 F.3d 157, 161 (2d Cir. 2003) (“We
agree . . . that it is inappropriate to employ the Mathews balancing test in criminal
cases.”). The danger is clear: more process does not sharpen the Constitution’s
vision for criminal justice, liberty, and order; it risks distorting that vision.

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Unlike the majority, then, I would use this opportunity to halt Mathews’s
slow drift into criminal proceedings and instead rely on the “careful balance” that
the Fourth Amendment strikes between “liberty and order.” Medina, 505 U.S. at
443. Based on that authority, and that authority alone, I would uphold the ex parte
search-warrant applications involved here as constitutional under the Warrants
Clause. See U.S. Const. amend. IV. Because those warrants were undoubtedly
based “upon probable cause, [were] supported by Oath or Affirmation, and
particularly describ[ed] the place to be searched, and the person or things to be
seized,” id., the requirements of the Fourth Amendment were clearly met. And
those requirements – not Mathews – are all that matter here, since “[t]he Fourth
Amendment was tailored explicitly for the criminal justice system, and its balance
between individual and public interests always has been thought to define the
‘process that is due’ for seizures of person or property in criminal cases.” Gerstein,
420 U.S. at 125 n.27.