UNITED STATES v. KNIGHTS

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
112 OCTOBER TERM, 2001
Syllabus
UNITED STATES v. KNIGHTS
certiorari to the united states court of appeals for
the ninth circuit
No. 00–1260. Argued November 6, 2001—Decided December 10, 2001
A California court’s order sentencing respondent Knights to probation
for a drug offense included the condition that Knights submit to search
at anytime, with or without a search or arrest warrant or reasonable
cause, by any probation or law enforcement officer. Subsequently, a
sheriff ’s detective, with reasonable suspicion, searched Knights’ apart-
ment. Based in part on items recovered, a federal grand jury indicted
Knights for conspiracy to commit arson, for possession of an unregis-
tered destructive device, and for being a felon in possession of ammu-
nition. In granting Knights’ motion to suppress, the District Court
held that, although the detective had “reasonable suspicion” to believe
that Knights was involved with incendiary materials, the search was
for “investigatory” rather than “probationary” purposes. The Ninth
Circuit affirmed.
Held: The warrantless search of Knights, supported by reasonable sus-
picion and authorized by a probation condition, satisfied the Fourth
Amendment. As nothing in Knights’ probation condition limits
searches to those with a “probationary” purpose, the question here is
whether the Fourth Amendment imposes such a limitation. Knights
argues that a warrantless search of a probationer satisfies the Fourth
Amendment only if it is just like the search at issue in Griffin v. Wis-
consin, 483 U. S. 868, i. e., a “special needs” search conducted by a pro-
bation officer monitoring whether the probationer is complying with
probation restrictions. This dubious logic—that an opinion upholding
the constitutionality of a particular search implicitly holds unconstitu-
tional any search that is not like it—runs contrary to Griffin’s express
statement that its “special needs” holding made it “unnecessary to con-
sider whether” warrantless searches of probationers were otherwise
reasonable under the Fourth Amendment. Id., at 878, 880. And this
Court need not decide whether Knights’ acceptance of the search condi-
tion constituted consent to a complete waiver of his Fourth Amendment
rights in the sense of Schneckloth v. Bustamonte, 412 U. S. 218, because
the search here was reasonable under the Court’s general Fourth
Amendment “totality of the circumstances” approach, Ohio v. Robinette,
519 U. S. 33, 39, with the search condition being a salient circumstance.
The Fourth Amendment’s touchstone is reasonableness, and a search’s
reasonableness is determined by assessing, on the one hand, the degree

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
113 Cite as: 534 U. S. 112 (2001)
Syllabus
to which it intrudes upon an individual’s privacy and, on the other, the
degree to which it is needed to promote legitimate governmental in-
terests. Wyoming v. Houghton, 526 U. S. 295, 300. Knights’ status as
a probationer subject to a search condition informs both sides of that
balance. The sentencing judge reasonably concluded that the search
condition would further the two primary goals of probation—rehabilita-
tion and protecting society from future criminal violations. Knights
was unambiguously informed of the search condition. Thus, Knights’
reasonable expectation of privacy was significantly diminished. In as-
sessing the governmental interest, it must be remembered that the
very assumption of probation is that the probationer is more likely than
others to violate the law. Griffin, supra, at 880. The State’s interest
in apprehending criminal law violators, thereby protecting potential
victims, may justifiably focus on probationers in a way that it does not
on the ordinary citizen. On balance, no more than reasonable suspicion
was required to search this probationer’s house. The degree of individ-
ualized suspicion required is a determination that a sufficiently high
probability of criminal conduct makes the intrusion on the individual’s
privacy interest reasonable. Although the Fourth Amendment ordi-
narily requires probable cause, a lesser degree satisfies the Constitution
when the balance of governmental and private interests makes such a
standard reasonable. See, e. g., Terry v. Ohio, 392 U. S. 1. The same
circumstances that lead to the conclusion that reasonable suspicion is
constitutionally sufficient also render a warrant requirement unnec-
essary. See Illinois v. McArthur, 531 U. S. 326, 330. Because the
Court’s holding rests on ordinary Fourth Amendment analysis that con-
siders all the circumstances of a search, there is no basis for examining
official purpose. Pp. 116–122.
219 F. 3d 1138, reversed and remanded.
Rehnquist, C. J., delivered the opinion for a unanimous Court. Sou-
ter, J., filed a concurring opinion, post, p. 122.
Malcolm L. Stewart argued the cause for the United
States. With him on the briefs were Solicitor General
Olson, Assistant Attorney General Chertoff, and Deputy
Solicitor General Dreeben.
Hilary A. Fox argued the cause for respondent. With her
on the brief was Barry J. Portman.*
*Briefs of amici curiae urging reversal were filed for the State of Cali-
fornia by Bill Lockyer, Attorney General, Robert R. Anderson, Chief As-
sistant Attorney General, Ronald A. Bass and Dane Gillette, Senior As-

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
114 UNITED STATES v. KNIGHTS
Opinion of the Court
Chief Justice Rehnquist delivered the opinion of the
Court.
A California court sentenced respondent Mark James
Knights to summary probation for a drug offense. The pro-
bation order included the following condition: that Knights
would “[s]ubmit his . . . person, property, place of resi-
dence, vehicle, personal effects, to search at anytime, with
or without a search warrant, warrant of arrest or reasonable
cause by any probation officer or law enforcement officer.”
Knights signed the probation order, which stated imme-
diately above his signature that “I HAVE RECEIVED
A COPY, READ AND UNDERSTAND THE ABOVE
TERMS AND CONDITIONS OF PROBATION AND
AGREE TO ABIDE BY SAME.” App. 49. In this case,
we decide whether a search pursuant to this probation con-
dition, and supported by reasonable suspicion, satisfied the
Fourth Amendment.
Three days after Knights was placed on probation, a Pa-
cific Gas & Electric (PG&E) power transformer and adjacent
Pacific Bell telecommunications vault near the Napa County
Airport were pried open and set on fire, causing an estimated
$1.5 million in damage. Brass padlocks had been removed
and a gasoline accelerant had been used to ignite the fire.
This incident was the latest in more than 30 recent acts of
vandalism against PG&E facilities in Napa County. Suspi-
cion for these acts had long focused on Knights and his
friend, Steven Simoneau. The incidents began after PG&E
sistant Attorneys General, and Laurence K. Sullivan, Supervising Deputy
Attorney General; for the Criminal Justice Legal Foundation by Kent S.
Scheidegger and Charles L. Hobson; and for the Center for Community
Interest by Andrew N. Vollmer and Steven Rosen.
Briefs of amici curiae urging affirmance were filed for the California
Public Defenders Association et al. by Kenneth I. Clayman; for the Na-
tional Association of Criminal Defense Lawyers by John Wesley Hall, Jr.,
and Lisa B. Kemler; and for the Rutherford Institute by James Joseph
Lynch, Jr., John W. Whitehead, and Steven H. Aden.

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
115 Cite as: 534 U. S. 112 (2001)
Opinion of the Court
had filed a theft-of-services complaint against Knights and
discontinued his electrical service for failure to pay his bill.
Detective Todd Hancock of the Napa County Sheriff ’s De-
partment had noticed that the acts of vandalism coincided
with Knights’ court appearance dates concerning the theft
of PG&E services. And just a week before the arson, a
sheriff ’s deputy had stopped Knights and Simoneau near a
PG&E gas line and observed pipes and gasoline in Simon-
eau’s pickup truck.
After the PG&E arson, a sheriff ’s deputy drove by
Knights’ residence, where he saw Simoneau’s truck parked
in front. The deputy felt the hood of the truck. It was
warm. Detective Hancock decided to set up surveillance
of Knights’ apartment. At about 3:10 the next morning,
Simoneau exited the apartment carrying three cylindrical
items. Detective Hancock believed the items were pipe
bombs. Simoneau walked across the street to the bank of
the Napa River, and Hancock heard three splashes. Simon-
eau returned without the cylinders and drove away in his
truck. Simoneau then stopped in a driveway, parked, and
left the area. Detective Hancock entered the driveway and
observed a number of suspicious objects in the truck: a Molo-
tov cocktail and explosive materials, a gasoline can, and two
brass padlocks that fit the description of those removed from
the PG&E transformer vault.
After viewing the objects in Simoneau’s truck, Detective
Hancock decided to conduct a search of Knights’ apart-
ment. Detective Hancock was aware of the search condition
in Knights’ probation order and thus believed that a warrant
was not necessary.1 The search revealed a detonation cord,
ammunition, liquid chemicals, instruction manuals on chem-
istry and electrical circuitry, bolt cutters, telephone pole-
climbing spurs, drug paraphernalia, and a brass padlock
stamped “PG&E.”
1 Hancock had seen a copy of the probation order when he was checking
Knights’ file in the Sheriff ’s Department office.

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
116 UNITED STATES v. KNIGHTS
Opinion of the Court
Knights was arrested, and a federal grand jury sub-
sequently indicted him for conspiracy to commit arson, for
possession of an unregistered destructive device, and for
being a felon in possession of ammunition. Knights moved
to suppress the evidence obtained during the search of his
apartment. The District Court held that Detective Hancock
had “reasonable suspicion” to believe that Knights was in-
volved with incendiary materials. App. to Pet. for Cert.
30a. The District Court nonetheless granted the motion to
suppress on the ground that the search was for “investiga-
tory” rather than “probationary” purposes. The Court of
Appeals for the Ninth Circuit affirmed. 219 F. 3d 1138
(2000). The Court of Appeals relied on its earlier decisions
holding that the search condition in Knights’ probation order
“must be seen as limited to probation searches, and must
stop short of investigation searches.” Id., at 1142–1143 (cit-
ing United States v. Ooley, 116 F. 3d 370, 371 (CA9 1997)).
The Supreme Court of California has rejected this dis-
tinction and upheld searches pursuant to the California pro-
bation condition “whether the purpose of the search is to
monitor the probationer or to serve some other law enforce-
ment purpose.” People v. Woods, 21 Cal. 4th 668, 681, 981
P. 2d 1019, 1027 (1999), cert. denied, 529 U. S. 1023 (2000).
We granted certiorari, 532 U. S. 1018 (2001), to assess the
constitutionality of searches made pursuant to this common
California probation condition.
Certainly nothing in the condition of probation suggests
that it was confined to searches bearing upon probationary
status and nothing more. The search condition provides
that Knights will submit to a search “by any probation officer
or law enforcement officer” and does not mention anything
about purpose. App. 49. The question then is whether the
Fourth Amendment limits searches pursuant to this proba-
tion condition to those with a “probationary” purpose.

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
117 Cite as: 534 U. S. 112 (2001)
Opinion of the Court
Knights argues that this limitation follows from our deci-
sion in Griffin v. Wisconsin, 483 U. S. 868 (1987). Brief for
Respondent 14. In Griffin, we upheld a search of a proba-
tioner conducted pursuant to a Wisconsin regulation per-
mitting “any probation officer to search a probationer’s
home without a warrant as long as his supervisor approves
and as long as there are ‘reasonable grounds’ to believe the
presence of contraband,” 483 U. S., at 870–871. The Wis-
consin regulation that authorized the search was not an ex-
press condition of Griffin’s probation; in fact, the regulation
was not even promulgated at the time of Griffin’s sentence.2
The regulation applied to all Wisconsin probationers, with
no need for a judge to make an individualized determina-
tion that the probationer’s conviction justified the need for
warrantless searches. We held that a State’s operation of
its probation system presented a “special need” for the
“exercise of supervision to assure that [probation] restric-
tions are in fact observed.” Id., at 875. That special need
for supervision justified the Wisconsin regulation and the
search pursuant to the regulation was thus reasonable. Id.,
at 875–880.
In Knights’ view, apparently shared by the Court of Ap-
peals, a warrantless search of a probationer satisfies the
Fourth Amendment only if it is just like the search at issue
in Griffin—i. e., a “special needs” search conducted by a pro-
bation officer monitoring whether the probationer is com-
plying with probation restrictions. This dubious logic—that
an opinion upholding the constitutionality of a particular
search implicitly holds unconstitutional any search that is
not like it—runs contrary to Griffin’s express statement that
its “special needs” holding made it “unnecessary to consider
whether” warrantless searches of probationers were other-
2 Griffin was placed on probation in September 1980, 483 U. S., at 870,
and the regulation was not promulgated until December 1981, id., at 871.

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
118 UNITED STATES v. KNIGHTS
Opinion of the Court
wise reasonable within the meaning of the Fourth Amend-
ment.3 Id., at 878, 880.
We now consider that question in assessing the constitu-
tionality of the search of Knights’ apartment. The Gov-
ernment, advocating the approach of the Supreme Court of
California, see Woods, supra, contends that the search sat-
isfied the Fourth Amendment under the “consent” rationale
of cases such as Zap v. United States, 328 U. S. 624 (1946),
and Schneckloth v. Bustamonte, 412 U. S. 218 (1973). In the
Government’s view, Knights’ acceptance of the search condi-
tion was voluntary because he had the option of rejecting
probation and going to prison instead, which the Government
argues is analogous to the voluntary decision defendants
often make to waive their right to a trial and accept a plea
bargain.4
We need not decide whether Knights’ acceptance of the
search condition constituted consent in the Schneckloth
sense of a complete waiver of his Fourth Amendment rights,
however, because we conclude that the search of Knights was
reasonable under our general Fourth Amendment approach
of “examining the totality of the circumstances,” Ohio v.
Robinette, 519 U. S. 33, 39 (1996), with the probation search
condition being a salient circumstance.
The touchstone of the Fourth Amendment is reasonable-
ness, and the reasonableness of a search is determined “by
3 The Wisconsin Supreme Court had held in Griffin that “probation
diminishes a probationer’s reasonable expectation of privacy—so that a
probation officer may, consistent with the Fourth Amendment, search a
probationer’s home without a warrant, and with only ‘reasonable grounds’
(not probable cause) to believe that contraband is present.” Id., at 872.
4 The Government sees our unconstitutional conditions doctrine as a
limitation on what a probationer may validly consent to in a probation
order. The Government argues that the search condition is not an uncon-
stitutional condition because waiver of Fourth Amendment rights “directly
furthers the State’s interest in the effective administration of its probation
system.” Brief for United States 22.

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
119 Cite as: 534 U. S. 112 (2001)
Opinion of the Court
assessing, on the one hand, the degree to which it intrudes
upon an individual’s privacy and, on the other, the degree to
which it is needed for the promotion of legitimate govern-
mental interests.” Wyoming v. Houghton, 526 U. S. 295,
300 (1999). Knights’ status as a probationer subject to a
search condition informs both sides of that balance. “Proba-
tion, like incarceration, is ‘a form of criminal sanction im-
posed by a court upon an offender after verdict, finding, or
plea of guilty.’ ” Griffin, supra, at 874 (quoting G. Killinger,
H. Kerper, & P. Cromwell, Probation and Parole in the Crim-
inal Justice System 14 (1976)). Probation is “one point . . .
on a continuum of possible punishments ranging from soli-
tary confinement in a maximum-security facility to a few
hours of mandatory community service.” 483 U. S., at 874.
Inherent in the very nature of probation is that probation-
ers “do not enjoy ‘the absolute liberty to which every citizen
is entitled.’ ” Ibid. (quoting Morrissey v. Brewer, 408 U. S.
471, 480 (1972)). Just as other punishments for criminal con-
victions curtail an offender’s freedoms, a court granting pro-
bation may impose reasonable conditions that deprive the
offender of some freedoms enjoyed by law-abiding citizens.
The judge who sentenced Knights to probation deter-
mined that it was necessary to condition the probation on
Knights’ acceptance of the search provision. It was reason-
able to conclude that the search condition would further the
two primary goals of probation—rehabilitation and protect-
ing society from future criminal violations.5 The probation
order clearly expressed the search condition and Knights
was unambiguously informed of it. The probation condition
5 Under California law, a probation condition is invalid if it (1) has no
relationship to the crime of which defendant was convicted; (2) relates to
conduct which in itself is not criminal; and (3) requires or forbids conduct
which is not reasonably related to future criminality. People v. Lent, 15
Cal. 3d 481, 485–486, 541 P. 2d 545, 548 (1975).

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
120 UNITED STATES v. KNIGHTS
Opinion of the Court
thus significantly diminished Knights’ reasonable expecta-
tion of privacy.6
In assessing the governmental interest side of the balance,
it must be remembered that “the very assumption of the
institution of probation” is that the probationer “is more
likely than the ordinary citizen to violate the law.” Griffin,
483 U. S., at 880. The recidivism rate of probationers is
significantly higher than the general crime rate. See U. S.
Dept. of Justice, Office of Justice Programs, Bureau of Justice
Statistics, Recidivism of Felons on Probation, 1986–89, pp. 1,
6 (Feb. 1992) (reporting that 43% of 79,000 felons placed on
probation in 17 States were rearrested for a felony within
three years while still on probation); U. S. Dept. of Justice,
Office of Justice Programs, Bureau of Justice Statistics, Pro-
bation and Parole Violators in State Prison, 1991, p. 3 (Aug.
1995) (stating that in 1991, 23% of state prisoners were pro-
bation violators). And probationers have even more of an
incentive to conceal their criminal activities and quickly dis-
pose of incriminating evidence than the ordinary criminal
because probationers are aware that they may be subject
to supervision and face revocation of probation, and possi-
ble incarceration, in proceedings in which the trial rights
of a jury and proof beyond a reasonable doubt, among other
things, do not apply, see Minnesota v. Murphy, 465 U. S. 420,
435, n. 7 (1984) (“[T]here is no right to a jury trial before
probation may be revoked”); 18 U. S. C. § 3583(e).
The State has a dual concern with a probationer. On the
one hand is the hope that he will successfully complete pro-
6 We do not decide whether the probation condition so diminished, or
completely eliminated, Knights’ reasonable expectation of privacy (or con-
stituted consent, see supra, at 118) that a search by a law enforcement
officer without any individualized suspicion would have satisfied the rea-
sonableness requirement of the Fourth Amendment. The terms of the
probation condition permit such a search, but we need not address the
constitutionality of a suspicionless search because the search in this case
was supported by reasonable suspicion.

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
121 Cite as: 534 U. S. 112 (2001)
Opinion of the Court
bation and be integrated back into the community. On the
other is the concern, quite justified, that he will be more
likely to engage in criminal conduct than an ordinary mem-
ber of the community. The view of the Court of Appeals
in this case would require the State to shut its eyes to the
latter concern and concentrate only on the former. But we
hold that the Fourth Amendment does not put the State to
such a choice. Its interest in apprehending violators of the
criminal law, thereby protecting potential victims of criminal
enterprise, may therefore justifiably focus on probationers in
a way that it does not on the ordinary citizen.
We hold that the balance of these considerations requires
no more than reasonable suspicion to conduct a search of this
probationer’s house. The degree of individualized suspicion
required of a search is a determination of when there is a
sufficiently high probability that criminal conduct is oc-
curring to make the intrusion on the individual’s privacy
interest reasonable. See United States v. Cortez, 449 U. S.
411, 418 (1981) (individualized suspicion deals “with prob-
abilities”). Although the Fourth Amendment ordinarily re-
quires the degree of probability embodied in the term “prob-
able cause,” a lesser degree satisfies the Constitution when
the balance of governmental and private interests makes
such a standard reasonable. See, e. g., Terry v. Ohio, 392
U. S. 1 (1968); United States v. Brignoni-Ponce, 422 U. S.
873 (1975). Those interests warrant a lesser than probable-
cause standard here. When an officer has reasonable sus-
picion that a probationer subject to a search condition is
engaged in criminal activity, there is enough likelihood
that criminal conduct is occurring that an intrusion on the
probationer’s significantly diminished privacy interests is
reasonable.
The same circumstances that lead us to conclude that
reasonable suspicion is constitutionally sufficient also ren-
der a warrant requirement unnecessary. See Illinois v.
McArthur, 531 U. S. 326, 330 (2001) (noting that general

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
122 UNITED STATES v. KNIGHTS
Souter, J., concurring
or individual circumstances, including “diminished expecta-
tions of privacy,” may justify an exception to the warrant
requirement).
Because our holding rests on ordinary Fourth Amendment
analysis that considers all the circumstances of a search,
there is no basis for examining official purpose. With the
limited exception of some special needs and administrative
search cases, see Indianapolis v. Edmond, 531 U. S. 32, 45
(2000), “we have been unwilling to entertain Fourth Amend-
ment challenges based on the actual motivations of indi-
vidual officers.” Whren v. United States, 517 U. S. 806, 813
(1996).
The District Court found, and Knights concedes, that the
search in this case was supported by reasonable suspicion.
We therefore hold that the warrantless search of Knights,
supported by reasonable suspicion and authorized by a condi-
tion of probation, was reasonable within the meaning of the
Fourth Amendment. The judgment of the Court of Appeals
is reversed, and the cause is remanded for further proceed-
ings consistent with this opinion.
It is so ordered.
Justice Souter, concurring.
As this case was originally presented to us, the dispute
centered on whether Knights’s agreement to the search con-
dition included in his terms of probation covered only those
searches with a probation-related purpose, or rather ex-
tended to searches with an investigatory or law-enforcement
purpose. At that time, the Government argued that Whren
v. United States, 517 U. S. 806 (1996), precluded any en-
quiry into the motives of the individual officers conduct-
ing the search. We now hold that law-enforcement searches
of probationers who have been informed of a search condi-
tion are permissible upon individualized suspicion of criminal
behavior committed during the probationary period, thus re-
moving any issue of the subjective intention of the investi-

534US1 Unit: $$U7 [04-10-03 15:11:56] PAGES PGT: OPIN
123 Cite as: 534 U. S. 112 (2001)
Souter, J., concurring
gating officers from the case. I would therefore reserve the
question whether Whren’s holding, that “[s]ubjective inten-
tions play no role in ordinary, probable-cause Fourth Amend-
ment analysis,” id., at 813, should extend to searches based
only upon reasonable suspicion.