United States v. Christian Estrella

FOR PUBLICATION

UNITED STATES COURT OF APPEALS
FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA, No. 22-10027

Plaintiff-Appellee, D.C. No.
3:19-cr-00517-
v. WHO-1

CHRISTIAN ALEJANDRO
ESTRELLA, OPINION

Defendant-Appellant.

Appeal from the United States District Court
for the Northern District of California
William Horsley Orrick, District Judge, Presiding

Argued and Submitted February 7, 2023
San Francisco, California

Filed June 6, 2023

Before: Jay S. Bybee and Patrick J. Bumatay, Circuit
Judges, and Richard D. Bennett,* Senior District Judge.

Opinion by Judge Bennett

*
The Honorable Richard D. Bennett, United States Senior District Judge
for the District of Maryland, sitting by designation.
2 UNITED STATES V. ESTRELLA

SUMMARY**

Criminal Law

The panel affirmed the district court’s denial of Christian
Alejandro Estrella’s motion to suppress evidence in a case in
which Estrella entered a conditional guilty plea to being a
felon in possession of a firearm and ammunition.
Estrella was arrested after two officers discovered a
handgun concealed in his vehicle. At the time of this
encounter, Estrella was a registered gang member on
California state parole, and was subject to a suspicionless
search condition that has been upheld by the Supreme Court.
Estrella argued on appeal that the officers did not have
advance knowledge that he was on parole at the time of this
encounter. It is firmly established that a search of a parolee
that complies with the terms of a valid search condition will
usually be deemed reasonable under the Fourth Amendment.
This Court has held that as a threshold requirement an officer
must know of a detainee’s parole status before that person
can be detained and searched pursuant to a parole condition.
But the Court has yet to specifically address how precise that
knowledge must be.
The panel held that a law enforcement officer must have
probable cause to believe that a person is on active parole
before conducting a suspicionless search or seizure pursuant
to a parole condition. Consistent with caselaw, and with
general Fourth Amendment principles, the officer must

**
This summary constitutes no part of the opinion of the court. It has
been prepared by court staff for the convenience of the reader.
 UNITED STATES V. ESTRELLA 3

possess advance knowledge of an applicable parole
condition before they may detain or search a parolee. That
knowledge must be particularized enough for the officer to
be aware that a parole condition applies and authorizes the
encounter. However, the officer need not be absolutely
certain, with ongoing day-by-day or minute-by-minute
awareness of the subject’s parole status. Instead, it is
sufficient for the officer to find, using the well-established
rules governing probable cause, that the individual to be
searched is on active parole, and an applicable parole
condition authorizes the search or seizure at issue.
Applying this standard, the panel concluded that the
arresting officers had probable cause to believe that Estrella
remained on active parole when he was detained and
searched. The panel further held that this encounter did not
violate California’s independent prohibition on arbitrary,
capricious, or harassing searches.

COUNSEL

Yevgeniy M. Parkman (argued) and Angela Chuang,
Assistant Federal Public Defenders; Jodi Linker, Federal
Public Defender; Federal Public Defender’s Office; San
Francisco, California; for Defendant-Appellant.
Molly Smolen (argued) and Kristina Green, Assistant United
States Attorneys; Matthew M. Yelovich, Appellate Section
Chief, Criminal Division; Stephanie M. Hinds, United States
Attorney; Office of the United States Attorney; San
Francisco, California; for Plaintiff-Appellee.
4 UNITED STATES V. ESTRELLA

OPINION

BENNETT, District Judge:

On August 14, 2019, Appellant Christian Alejandro
Estrella (“Estrella”) was arrested as a felon in unlawful
possession of a firearm after two officers discovered a
handgun and ammunition concealed in his vehicle. At the
time of this encounter, Estrella was a registered gang
member on California state parole, and was subject to a
suspicionless search condition that has been upheld by the
Supreme Court. See Cal. Penal Code § 3067(b)(3); see also
Samson v. California, 547 U.S. 843, 857 (2006). After
entering a plea of guilty and preserving his right to appeal,
Estrella appeals the district court’s denial of his motion to
suppress evidence, arguing that the officers did not have
advance knowledge that he was on parole at the time of this
encounter. We have jurisdiction pursuant to 28 U.S.C. §
1291, and we affirm.
It is firmly established that “[a] search of a parolee that
complies with the terms of a valid search condition will
usually be deemed reasonable under the Fourth
Amendment.” United States v. Cervantes, 859 F.3d 1175,
1183 (9th Cir. 2017). As a threshold requirement, we have
held that “an officer must know of a detainee’s parole status
before that person can be detained and searched pursuant to
a parole condition.” Moreno v. Baca, 431 F.3d 633, 641 (9th
Cir. 2005). However, this Court has yet to specifically
address how precise that knowledge must be.
For the reasons articulated below, we now hold that a law
enforcement officer must have probable cause to believe that
a person is on active parole before he may be detained and
searched pursuant to a parole condition. Although a law
 UNITED STATES V. ESTRELLA 5

enforcement officer must have “advance knowledge” that
the detainee remains on active parole, United States v.
Cesares, 533 F.3d 1064, 1076 (9th Cir. 2008), the officer
need not “know to an absolute certainty,” with precise day-
by-day or minute-by-minute information of the detainee’s
parole status, People v. Douglas, 193 Cal. Rptr. 3d 79, 89
(Cal. Ct. App. 2015). It is sufficient for the officer to
determine, using the well-established rules governing
probable cause, that the individual to be detained and
searched is on active parole, and that an applicable parole
condition authorizes the challenged search or seizure.
Applying this standard, we conclude that the arresting
officers had probable cause to believe that Estrella remained
on active parole when he was detained and searched on
August 14, 2019. We further hold that this encounter did not
violate California’s independent prohibition on arbitrary,
capricious, or harassing searches. Accordingly, we affirm
the denial of Estrella’s motion to suppress.
BACKGROUND
As this appeal arises from the denial of a motion to
suppress, we review the facts set forth in the district court’s
order denying that motion, and the declarations, exhibits,
and footage upon which that order was founded. “We review
the denial of a motion to suppress de novo, and any
underlying findings of fact for clear error.” United States v.
Vandergroen, 964 F.3d 876, 878 (9th Cir. 2020). In 2015,
Estrella stipulated to a gang-related sentence enhancement
following a conviction for Obstructing or Resisting an
Executive Officer, in violation of Cal. Penal Code § 69. As
part of his gang registration requirements, Estrella admitted
that he had been a member of the Angelino Heights Sureños,
6 UNITED STATES V. ESTRELLA

a criminal gang based in Santa Rosa, California, for five
years.
Following his release from prison, Estrella relocated to
Lakeport, California. On July 2, 2018, Estrella visited the
Lakeport Police Department (“LPD”) to register as a
convicted gang member, as required by Cal. Penal Code §
186.30. The police department informed Officer Tyler
Trouette (“Trouette”), LPD’s gang specialist and a member
of the Lake County Gang Task Force,1 that Estrella was on
parole and was registered as a member of the Angelino
Heights Sureños gang. Trouette familiarized himself with
Estrella’s “criminal history and his previous gang-related
convictions.” However, the record is silent as to whether
Trouette personally became aware of the date Estrella’s
parole was set to conclude.
On July 3, 2018, one day after Estrella completed his
gang registration, Trouette visited Estrella at his home.
According to the Government, Trouette and Estrella
discussed Estrella’s parole conditions, and confirmed that he
was prohibited from associating with a gang or wearing gang
attire. In his declaration, cited by the district court, Trouette
describes this conversation as follows:

I told Mr. Estrella that I had not yet reviewed
his gang conditions, but I presumed that they
included that he could not associate with

1
The Lake County Gang Task Force “is a county-wide joint task force
with participants from several law enforcement agencies operating in
Lake County.” The task force held monthly meetings, during which its
members were apprised of “gang activity in Lake County as well as
individual gang members and law enforcement efforts relating to crimes
perpetrated by gangs.” Its members were also responsible for
investigating gang activity on behalf of their local police department.
 UNITED STATES V. ESTRELLA 7

other gang members or possess things that are
associated with the gang. Mr. Estrella said
that he knew all the rules. Later in the
conversation, I told him that LPD had
knowledge of the Angelino[] Heights
Sure[ñ]os and that he would not get away
with wearing Oakland Athletics’ hats or other
things like that. Based on my training and
experience, I know Oakland Athletics’ hats
are commonly worn by members of the
Angelino[] Heights Sure[ñ]os because, to
members of the gang, the ‘A’ on the hat
signifies ‘Angelino.’

Thereafter, between July 2018 and August 2019, Trouette
“had several additional conversations with . . . Estrella’s
parole officer about . . . Estrella.” Through these
conversations, the parole officer informed Trouette of
Estrella’s “conditions of parole and gang terms.”
Additionally, in April 2019, the parole officer informed
Trouette that Estrella “had violated his parole by committing
a battery.”2 He did not indicate at any point that Estrella’s
parole was soon to expire.
This appeal arises from an encounter between Trouette
and Estrella on August 14, 2019—fourteen months after
Trouette learned that Estrella had been placed on parole, and
only four months after Trouette was informed that Estrella
had violated his parole conditions. At the time, Trouette was
the Field Training Officer for Officer Ryan Cooley
(“Cooley”), a new officer enrolled in LPD’s field training

2
The record does not suggest that any action was taken as a result of this
alleged parole violation.
8 UNITED STATES V. ESTRELLA

program. At about 8:00 p.m., Trouette and Cooley were
driving westbound on Lakeport’s Armstrong Street in a
marked patrol car. As they passed Polk Street, Trouette saw
Estrella standing outside his residence next to a white Honda
Accord and decided “to check up on him and verify that he
was abiding by the terms of his parole.” However, he
declined to inform Cooley of Estrella’s parole conditions, as
he wanted the trainee to “find the relevant information
through his own investigation.”
The officers turned around and drove up Polk Street. As
they approached Estrella, Trouette observed that the
defendant was wearing an Oakland Athletics hat, which he
recognized as a sign of the Angelino Heights Sureños gang
and a violation of Estrella’s parole condition prohibiting
gang symbols and attire. The officers parked “several car
lengths” down the street and approached on foot, in full
police uniform and with their guns visible. Estrella walked
towards them and met them partway.3
A short conversation ensued. Cooley asked Estrella
“what he was up to.” Estrella explained that he had just
returned home from work and was working on his car.
Trouette instructed Cooley to inform dispatch of their
location, and Cooley stepped away to convey this
information. While Cooley was speaking to dispatch,

3
The parties contest whether the officers directed Estrella to stop or to
approach. This appears to be an unresolved factual dispute: Estrella
alleges in his declaration that the officers “indicated to [him] to stop,”
while Officers Trouette and Cooley attest in their declarations that they
gave no such order, and the officers’ body camera footage begins after
this point. The district court observed and highlighted this dispute but
declined to resolve it. As we ultimately hold that this encounter was a
valid parole seizure pursuant to Cal. Penal Code § 3067, we need not
reach this issue.
 UNITED STATES V. ESTRELLA 9

Estrella’s mother came out of the house, and Trouette
inquired about the Oakland Athletics hat. Estrella described
it as a “work hat,”4 but Trouette reiterated that Estrella was
“flying [his] Angelino Heights ‘A,’” and that he “shouldn’t
be wearing [it].”
About ninety seconds after the encounter began, Cooley
returned to the scene. Cooley asked Estrella whether he had
identification and whether he was on probation or parole.
Estrella confirmed that he was on parole and volunteered his
driver’s license, and Cooley again contacted dispatch to
verify this information. Dispatch confirmed that Estrella was
on probation until October 2019, that he was on California
parole until 2020, and that he had registered as a convicted
felon and a member of the Angelino Heights Sureños gang.
Thereafter, the officers searched his person and his vehicle.
Estrella informed Trouette that he had a gun in the car, and
the officer promptly placed him under arrest. Cooley found
a loaded Ruger 9mm handgun and nine rounds of
ammunition in the car’s center console.
On October 10, 2019, Estrella was indicted for being a
felon in possession of a firearm and ammunition, in violation
of 18 U.S.C. § 922(g)(1). On January 31, 2020, Estrella
moved to suppress the handgun found in the car. The parties’
arguments turned primarily on whether the encounter was
valid as a parole search and seizure, pursuant to Cal. Penal
Code § 3067. Estrella claimed that the roadside encounter
was a Fourth Amendment seizure, and that this Court’s
precedent requires an officer to have “actual knowledge” of
an applicable parole condition before they may detain and
search a parolee. As Trouette was unaware of the precise end

4
Estrella explained in his declaration that he was wearing this hat to keep
his hair out of his eyes as he worked on his car.
10 UNITED STATES V. ESTRELLA

date of Estrella’s parole, Estrella argued that Trouette did not
possess the requisite knowledge to conduct a parole search
or seizure. The Government responded by arguing that
Trouette had a “reasonable belief” in Estrella’s parole status
due to his meeting with Estrella, his conversations with
Estrella’s parole officer, his knowledge of a recent parole
violation, and his experience with the standard terms of
California parole. In the alternative, the Government argued
that Estrella had not been “seized” for Fourth Amendment
purposes before acknowledging that he was on parole.
Following a hearing, the district court denied Estrella’s
motion to suppress. The court assumed without deciding that
a seizure had occurred but found that it was valid as a parole
seizure regardless. The court concluded that Trouette had a
“reasonable belief” in Estrella’s parole status and that “this
level of knowledge is sufficient” to justify a suspicionless
parole seizure under Cal. Penal Code § 3067, as construed in
Samson, 547 U.S. at 846–47. Estrella entered a guilty plea
pursuant to Fed. R. Crim. P. Rule 11(a)(2), preserving his
right to appeal the denial of his motion to suppress. On
January 27, 2022, he was sentenced to time served followed
by a three-year period of supervised release and referred to
the district court’s alternatives to incarceration program. He
was also directed to forfeit the firearm and ammunition
seized during the search, and to pay a $100 special
assessment.
This appeal followed.
STANDARD OF REVIEW
We review the denial of a motion to suppress evidence
de novo. United States v. Peterson, 995 F.3d 1061, 1064 (9th
Cir. 2021), cert. denied, 142 S. Ct. 472 (2021); United States
v. Torres, 828 F.3d 1113, 1118 (9th Cir. 2016); United States
 UNITED STATES V. ESTRELLA 11

v. Forrester, 512 F.3d 500, 506 (9th Cir. 2008). The district
court’s underlying factual findings are reviewed for clear
error, Peterson, 995 F.3d at 1064, while pure questions of
law and mixed questions of law and fact are reviewed de
novo. See United States v. Scott, 705 F.3d 410, 414–15 (9th
Cir. 2012). Additionally, this Court may affirm the denial of
a motion to suppress “on any basis supported by the record.”
United States v. McClendon, 713 F.3d 1211, 1218 (9th Cir.
2013).
DISCUSSION
The Fourth Amendment to the United States
Constitution protects “[t]he right of the people to be secure
in their persons, houses, papers, and effects, against
unreasonable searches and seizures.” U.S. Const. amend.
IV; see also Carpenter v. United States, 138 S. Ct. 2206,
2214 (2018) (“[T]he Amendment seeks to secure ‘the
privacies of life’ against ‘arbitrary power.’” (quoting Boyd
v. United States, 116 U.S. 616, 630 (1886))). It is firmly
established that searches or seizures “conducted outside the
judicial process, without prior approval by judge or
magistrate, are per se unreasonable under the Fourth
Amendment—subject only to a few specifically established
and well delineated exceptions.” United States v. Brown, 996
F.3d 998, 1004 (9th Cir. 2021) (quoting Minnesota v.
Dickerson, 508 U.S. 366, 372 (1993)). Among these
exceptions, “[a] search of a parolee that complies with the
terms of a valid search condition will usually be deemed
reasonable under the Fourth Amendment.” Cervantes, 859
F.3d at 1183; United States v. Job, 871 F.3d 852, 859 (9th
Cir. 2017); United States v. King, 736 F.3d 805, 810 (9th Cir.
2013).
12 UNITED STATES V. ESTRELLA

The State of California imposes expansive search
conditions on its parolees. Pursuant to Cal. Penal Code §
3067(b)(3), every parolee under the state’s supervision “is
subject to search or seizure . . . at any time of the day or
night, with or without a search warrant or with or without
cause.” In Samson v. California, the Supreme Court held that
this broad provision satisfies the mandates of the Fourth
Amendment, as the state’s interests in public safety and
reintegration outweigh the privacy interests of its parolees.
547 U.S. 843, 857 (2006). As parole is a “an established
variation on imprisonment” subject to strict monitoring and
behavioral conditions, id. at 850 (quoting Morrissey v.
Brewer, 408 U.S. 471, 477 (1972)), parolees’ expectations
of privacy are “severely diminished . . . by virtue of their
status alone,” id. at 852. Those limited privacy interests are
comprehensively outmatched by the state’s “‘overwhelming
interest’ in supervising parolees” to reduce recidivism and
“promot[e] reintegration and positive citizenship.” Id. at 853
(quoting Penn. Bd. of Probation & Parole v. Scott, 524 U.S.
357, 365 (1998)).
Nevertheless, law enforcement officers do not possess
unfettered discretion to detain and search suspected parolees.
Two principles constrain an officer’s authority to conduct a
suspicionless parole search or seizure pursuant to Cal. Penal
Code § 3067(b)(3). See United States v. Korte, 918 F.3d 750,
754 n.1 (9th Cir. 2019); United States v. Grandberry, 730
F.3d 968, 975 (9th Cir. 2013). First, law enforcement must
know that the subject is on active parole before initiating a
search or seizure pursuant to a parole condition. Moreno,
431 F.3d at 641. Second, the encounter must not violate
California’s statutory prohibition on “arbitrary, capricious or
harassing” searches. Korte, 918 F.3d at 754 n.1; see Cal.
Penal Code § 3067(d) (“It is not the intent of the Legislature
 UNITED STATES V. ESTRELLA 13

to authorize law enforcement officers to conduct searches for
the sole purpose of harassment.”).
Estrella invokes both limitations to argue that his
detention and search violate the Fourth Amendment.5 First,
Estrella claims that an officer must possess “actual
knowledge” of the suspect’s parole status before conducting
a suspicionless search or seizure pursuant to a parole
condition. Applying this framework, he argues that Trouette
did not know that Estrella was on active parole, as Trouette
did not know precisely when Estrella’s parole had begun or
when it was scheduled to conclude. Second, Estrella argues
this encounter was arbitrary, capricious, or harassing, as
Trouette was motivated to train Cooley, not by legitimate
law enforcement concerns. Both arguments fail. For the
reasons detailed below, we hold that an officer must have
probable cause to believe that a person is on active parole
before initiating a parole search, and that the information
known to Trouette at the time of the encounter satisfied this
requirement. Additionally, we hold that this encounter does

5
The district court assumed without deciding that Estrella was detained.
Generally, whether a consensual encounter escalates into a seizure
depends on the totality of the circumstances surrounding the encounter.
Brown, 996 F.3d at 1005; accord United States v. Mendenhall, 446 U.S.
544, 557–58 (1980) (“[A] person has been ‘seized’ within the meaning
of the Fourth Amendment only if, in view of all of the circumstances
surrounding the incident, a reasonable person would have believed that
he was not free to leave.”). As discussed above, there is an outstanding
factual dispute as to whether the officers commanded Estrella to stop. As
this dispute is inextricable from the totality of the circumstances, we
assume without deciding that a seizure occurred, and address only the
parole search exception. Cf. McClendon, 713 F.3d at 1218 (holding that
this Court may affirm the denial of a motion to suppress “on any basis
supported by the record”).
14 UNITED STATES V. ESTRELLA

not violate California’s prohibition on arbitrary, capricious,
and harassing searches.
I. Knowledge Prerequisite to Parole Searches
The parties dispute whether Trouette had sufficient
knowledge of Estrella’s parole status to detain and search
him pursuant to Cal. Penal Code § 3067. Broadly, the Fourth
Amendment requires officers to have knowledge of the facts
justifying a search or seizure at the time of the challenged
encounter. See Moreno, 431 F.3d at 639; see, e.g., Job, 871
F.3d at 860; United States v. Magallon-Lopez, 817 F.3d 671,
675 (9th Cir. 2016). Those same principles require that “an
officer must know of a detainee’s parole status before that
person can be detained and searched pursuant to a parole
condition.” Moreno, 431 F.3d at 641; see also People v.
Sanders, 73 P.3d 496, 505 (2003). An officer cannot
retroactively validate a search or seizure conducted without
suspicion by later discovering that the person searched was
on active parole and subject to an applicable search
condition. Moreno, 431 F.3d at 641; accord Fitzgerald v.
City of Los Angeles, 485 F. Supp. 2d 1137, 1143 (C.D. Cal.
2007) (“[A]dvance knowledge of a parolee’s status is critical
to the constitutionality of a suspicionless search of a parolee.
. . . If the officer learns of this status after the suspicionless
search has commenced, the search is in violation of the
Fourth Amendment.”).
While we have held that an officer must possess advance
knowledge of a parolee’s status to conduct a parole search,
we have yet to decide how precise that knowledge must be.
As the LPD’s gang specialist, Trouette was familiar with the
effect of gang-related convictions and the typical length of
California parole terms. Prior to the encounter on August 14,
2019, he had spoken with Estrella personally, familiarized
 UNITED STATES V. ESTRELLA 15

himself with Estrella’s case, and held several conversations
with Estrella’s parole officer to discuss his “conditions of
parole and gang terms.” During these conversations,
Trouette learned that Estrella had been on parole since
roughly July 2018, that Estrella was prohibited from
associating with gang members or wearing gang attire, and
that Estrella had violated a parole condition in April 2019.
However, the record is silent as to whether he was ever
informed of the precise date that Estrella’s parole
commenced, or when it was scheduled to conclude.6
Accordingly, this case raises a question of degree: What
level of prior knowledge must an officer possess to initiate a
suspicionless parole search?
***
Estrella relies on United States v. Caseres, in which we
held that California’s statutory search condition “validates a
search only if the police had advance knowledge that the
search condition applied.” 533 F.3d 1064, 1075–76 (9th Cir.
2008). In Caseres, the defendant was arrested following a
foot chase, and admitted to the arresting officer that he was
on parole. Id. at 1067–68, 1074. Sometime later, officers

6
It is undisputed that Cooley was entirely unaware of Estrella’s parole
status at the time of the challenged encounter. However, Trouette’s
knowledge is imputed to Cooley under the collective knowledge
doctrine. See United States v. Villasenor, 608 F.3d 467, 475 (9th Cir.
2010) (holding that knowledge may be imputed between officers (1)
“where law enforcement agents are working together in an investigation
but have not explicitly communicated the facts each has independently
learned,” or (2) “where an officer . . . with direct personal knowledge of
all the facts necessary to give rise to reasonable suspicion . . . directs or
requests that another officer . . . conduct a stop, search, or arrest”
(quoting United States v. Ramirez, 473 F.3d 1026, 1032–33 (9th Cir.
2007))).
16 UNITED STATES V. ESTRELLA

searched the defendant’s car without any reason to believe it
contained evidence of a crime, and discovered a firearm and
ammunition that led to charges as a felon in possession. Id.
at 1068, 1076. The district court denied the defendant’s
motion to suppress, and the defendant entered a conditional
guilty plea. Id. at 1068. We upheld the arrest but found the
search unconstitutional. Id. at 1069, 1076.7 Although the
officer had testified that he “was aware Caseres was on
parole prior to ordering the search of his vehicle,” the
government had failed to show that the officer “was aware
that Cal. Pen. Code § 3067 applied.” Id. at 1076. We
specifically noted that the record was devoid of evidence that
the officer knew the defendant “was a parolee of the State of
California, to whom § 3067(a) applied,” or that the officer
“knew whether Caseres’s prior offense had been committed
prior to January 1, 1997,” as required by the statute. Id.
Estrella analogizes Caseres to argue that the “advance
knowledge” requirement set forth by our caselaw demands
nothing short of “actual knowledge.” He proposes a rigorous
standard under which “[a]n officer does not know that a
person is presently on parole unless the facts known to the
officer require that conclusion.” Any lesser rule, he argues,
would depart from our precedent and derogate from the
privacy protections embodied by the Fourth Amendment,

7
The district court in Caseres held the search was justified as a search
incident to arrest or an inventory search, each separate exceptions to the
warrant requirement. Id. at 1070; see South Dakota v. Opperman, 428
U.S. 364, 372 (1976) (inventory search); United States v. Robinson, 414
U.S. 218, 235 (1973) (search incident to arrest). We found both
exceptions inapplicable, as the search of Caseres’ vehicle “was too far
removed in time from the arrest” to qualify as a search incident to arrest,
and that it did not “serve any community caretaking purpose,” as
required for an inventory search. Caseres, 533 F.3d at 1074.
 UNITED STATES V. ESTRELLA 17

encouraging unfettered searches of suspected parolees.
Applying this standard, Estrella argues that Trouette lacked
advance knowledge of Estrella’s parole status, as he did not
know the precise end date of Estrella’s parole and did not
call dispatch to update this information.
This argument reads too much into our caselaw. The
“advance knowledge” threshold imposed by our
jurisprudence is not an “actual knowledge” requirement.
Rather, it addresses the general prohibition on retroactive
justifications. While we have held that the parole search
exception “validates a search only if the police had advance
knowledge that the search condition applied,” Caseres, 533
F.3d at 1075–76, the thrust and import of this rule is that
officers “cannot retroactively justify a suspicionless search
and arrest on the basis of an after-the-fact discovery of an
arrest warrant or a parole condition.” Moreno, 431 F.3d at
641; accord Fitzgerald, 485 F. Supp. 2d at 1142 (“[A]
knowledge-first requirement is appropriate to deter future
police misconduct and to effectuate the Fourth
Amendment’s guarantee against unreasonable searches and
seizures” (quoting Sanders, 73 P.3d at 504)). Although these
cases found the officer’s lack of advance knowledge
dispositive, they did not discuss or decide the standard for
knowledge. Such a standard should not be assumed. See
United States v. Kirilyuk, 29 F.4th 1128, 1134 (9th Cir.
2022) (“[C]ases are not precedential for propositions not
considered, or for matters that are simply assumed.” (cleaned
up)).
Nor do we read the facts of Caseres to demand such a
rigorous requirement. The relevant issue in Caseres was
whether “the search of Caseres’s car can be justified after the
fact as a parole search.” 533 F.3d at 1075. As noted above,
the officer in that case encountered the defendant during a
18 UNITED STATES V. ESTRELLA

routine traffic stop, arrested him after an altercation and a
foot-chase, and searched his vehicle without suspicion. Id. at
1067–68. The government’s central shortcoming was its
failure to establish that the officer “was aware that Cal. Pen.
Code § 3067 applied before he ordered the search of
Caseres’s car,” as he did not know “when, and in what state,
Caseres committed the crime for which he was paroled,” or
whether he had committed an offense within the ambit of the
statute. Id. at 1076.8 There is no such uncertainty here.
Officer Trouette knew Estrella had been placed on California
parole, was familiar with his criminal history,9 spoke with
him about his parole conditions, maintained contact with his
parole officer, and learned of a recent parole violation. These
facts are sufficient to bring this case outside the
contemplation of Caseres.
As we are not constrained by our precedent, we decline
to adopt the inflexible standard Estrella proposes, which
would create practical problems for everyday police work. If
the standard is “actual knowledge,” with no latitude for
uncertainty, officers must possess “up-to-the-minute

8
Furthermore, the government argued that the search of Caseres’ vehicle
was either a search incident to arrest or an inventory search, and the
district court ruled exclusively on that basis. Id. at 1074–75. The
government did not invoke the parole search exception until appeal. Id.
at 1070, 1075. In this important sense, any application of the parole
search exception would have been retroactive. Comparatively, the
encounter at issue in this case was justified, start to finish, as a parole
detention and a parole search.
9
Estrella does not appear to contend that Trouette did not know whether
he had committed his crime before January 1, 1997. This is for good
reason. Estrella’s gang registration paperwork indicates that he had been
arrested in 2015 and 2018 for the conviction that placed him on parole.
Additionally, as Estrella was born in 1994, he would have been only
about three years old by the time specified in Cal. Penal Code § 3067.
 UNITED STATES V. ESTRELLA 19

information” of a parolee’s status before proceeding with a
routine compliance check. Cf. Douglas, 193 Cal. Rptr. 3d at
89. It is easy to imagine a scenario where Trouette sees
Estrella’s name on a parole list and elects to search him four
days later rather than four months—without double-
checking police records, but with every reason to believe that
he remains on parole. It is equally easy to conceive of a
scenario where Trouette knows of the exact date Estrella’s
parole was scheduled to end—but Estrella’s parole is
terminated early, and Trouette conducts a compliance check
the following day. Under Estrella’s proposed standard, either
scenario would be constitutionally infirm, and any
imperfection in an officer’s knowledge would be fatal. Such
a result is incompatible with the Fourth Amendment, which
calls for reasonable determinations, and does not demand
certainty. See Hill v. California, 401 U.S. 797, 804 (1971)
(“[S]ufficient probability, not certainty, is the touchstone of
reasonableness under the Fourth Amendment.”); see, e.g.,
Florida v. Harris, 568 U.S. 237, 244 (2013); Ohio v.
Robinette, 519 U.S. 33, 39 (1996); Florida v. Bostick, 501
U.S. 429, 439 (1991); Illinois v. Gates, 462 U.S. 213, 232
(1983).10

10
The Government responds to Estrella’s argument in part by insisting
that a person acting “with an awareness of the high probability of the
existence of the fact in question” is functionally acting with knowledge.
United States v. Jewell, 532 F.2d 697, 700 (9th Cir. 1976). Although we
decline to adopt Estrella’s proposed standard, we reject this
counterargument as an inaccurate construction of our precedent on the
definition of “knowledge.” As we have clarified, the “high probability of
awareness” standard only applies “in situations where the evidence
justifies an argument of willful blindness,” and “has never been used in
this circuit as a definition of actual knowledge.” United States v. Aguilar,
80 F.3d 329, 332 (9th Cir. 1996).
20 UNITED STATES V. ESTRELLA

***
The Government suggests that we adopt the standard
outlined in People v. Douglas, in which a California
appellate court held that “[a]n officer ‘knows’ a subject is on
[parole] if the officer’s belief is objectively reasonable.” 193
Cal. Rptr. 3d 79, 89–90 (Cal. Ct. App. 2015). In Douglas, an
officer on patrol detained a probationer and searched his
vehicle without probable cause, discovering a firearm that
led to felon in possession charges. Id. at 82–83. The officer
did not consult the police database to verify that the
defendant was on probation before conducting the search. Id.
However, he had arrested the defendant for weapon
possession two years prior, and he recalled seeing the
defendant’s name on a list of probationers “within the
preceding two months.” Id. The trial court denied the
defendant’s motion to suppress, and the appellate court
affirmed. Id. at 83–84. At the outset, the court rejected the
argument that an officer must have “absolute certainty”
predicated on “up-to-the-minute information” to possess
“advance knowledge” of an applicable search condition. Id.
at 89.11 Instead, the court analogized state and federal Fourth

11
Douglas dealt with a more stringent requirement than we address here.
“Suspicionless searches are lawful in California for both probationers
and parolees, so long as they are not conducted arbitrarily, capriciously,
or for harassment.” Id. at 85 (citing People v. Bravo, 738 P.2d 336, 342
(Cal. 1987)). However, while “a suspicionless search condition is
imposed on all parolees by statute,” courts “individualize the terms and
conditions of probation to fit the offender.” Id. at 87. Accordingly, a
probation search requires a more granular degree of knowledge than a
parole search: “[I]n the case of probation searches, the officer must have
some knowledge not just of the fact someone is on probation, but of the
existence of a search clause broad enough to justify the search at issue.”
Id. (citing Bravo, 738 P.3d at 338–41). As the government seeks to use
 UNITED STATES V. ESTRELLA 21

Amendment caselaw to hold that the officer’s belief in the
defendant’s status need only be “objectively reasonable in
the totality of the circumstances.” Id. at 89–90. Given the
officer’s “knowledge of the law pertaining to firearms
offenses . . . and the usual length of [probation],”
corroborated by his familiarity with the defendant and recent
confirmation of his probationer status, it was reasonable for
him to believe that the defendant was still on probation. Id.
at 93–94.
This framework is consistent with generally applicable
Fourth Amendment principles. Generally, the predicate
circumstances that justify a challenged search or seizure
must be known to the officer at the time of the challenged
encounter. See Moreno, 431 F.3d at 639, 641; accord Scott
v. United States, 436 U.S. 128, 137 (1978) (“[A]lmost
without exception in evaluating alleged violations of the
Fourth Amendment the Court has first undertaken an
objective assessment of an officer’s actions in light of the
facts and circumstances then known to him.”).
Consequently, officers cannot manufacture probable cause
or an exception to the warrant requirement based on facts
that are discovered during or after a search. Moreno, 431
F.3d at 639, 641; see, e.g., Job, 871 F.3d at 859, 863 (officers
found search waiver after conducting pat-down search);
United States v. Luckett, 484 F.2d 89, 90–91 (9th Cir. 1973)
(officer discovered outstanding traffic warrant after
detaining defendant). Thus, in nearly every situation,
officers must have “advance knowledge” of the
circumstances that justify a search or seizure.

Estrella’s parole status to justify the seizure, that additional granularity
is unnecessary here.
22 UNITED STATES V. ESTRELLA

However, the Fourth Amendment does not require
perfection. As “the ultimate touchstone of the Fourth
Amendment is reasonableness,” reasonable mistakes of fact
or law do not invalidate a search or seizure that would
otherwise satisfy constitutional muster. Heien v. North
Carolina, 574 U.S. 54, 60–61 (2014) (quoting Riley v.
California, 573 U.S. 373, 381 (2014)) (internal quotations
omitted). Accordingly, an officer’s reasonable belief that the
predicate circumstances exist to conduct a search or seizure
is often constitutionally sufficient. See, e.g., Heien, 574 U.S.
at 60–61, 66–68 (upholding traffic stop based on officer’s
reasonable but mistaken belief that the defendant’s conduct
was prohibited by state law); Illinois v. Rodriguez, 497 U.S.
177, 179–80, 189 (1990) (upholding consent search based on
officer’s reasonable but mistaken belief that the individual
had authority to consent); Hill v. California, 401 U.S. 797,
802–05 (1971) (upholding arrest where officers mistakenly
arrested individual matching suspect’s description); United
States v. Sledge, 650 F.2d 1075, 1077 (9th Cir. 1981)
(upholding search of apartment based on officer’s
reasonable but mistaken belief that the premises had been
abandoned). This flexible evaluation reflects the idea that the
exclusionary rule is meant to deter police misconduct—not
to penalize officers who act reasonably. See United States v.
Leon, 468 U.S. 897, 916 (1984).
Nevertheless, although we concur with the principles
articulated in Douglas, we conclude that probable cause is a
more principled standard to apply. “Determining the
reasonableness of a particular search involves balancing the
degree to which the search intrudes upon an individual’s
privacy against the degree to which the search is needed to
further legitimate governmental interests.” Ioane v. Hodges,
939 F.3d 945, 953 (9th Cir. 2018); accord Bell v. Wolfish,
 UNITED STATES V. ESTRELLA 23

441 U.S. 520, 559 (1979) (“In each case it requires a
balancing of the need for the particular search against the
invasion of personal rights that the search entails.”). The
statute at issue here confers broad discretion to detain and
search parolees “at any time of the day or night, with or
without a search warrant or with or without cause.” Cal.
Penal Code § 3067(b)(3). Applied to parolees, whose
expectations of privacy are diminished, this provision is
reasonable. However, the precondition at issue in this case
safeguards the rights of third parties, who retain their privacy
interests in full. Granting officers too much latitude to search
individuals who are believed to be on parole would create a
substantial risk that third parties are searched or seized based
on faulty assumptions about their parole status, and without
any suspicion of criminal activity. Unfettered discretion of
that nature is precisely what the Fourth Amendment
proscribes. See Arizona v. Gant, 556 U.S. 332, 345 (2009).
Probable cause is better calibrated to reduce the
likelihood of such intrusions. “The rule of probable cause is
a practical, nontechnical conception affording the best
compromise that has been found for accommodating these
often opposing interests.” Motley v. Parks, 432 F.3d 1072,
1080 (9th Cir. 2005) (quoting Brinegar v. United States, 338
U.S. 160, 176 (1949)), overruled on other grounds by United
States v. King, 687 F.3d 1189 (9th Cir. 2012). This
framework has been developed through decades of caselaw
and is familiar to law enforcement officers and judges across
this circuit. The principled protections that it offers
adequately balance “the individual’s right to liberty and the
State’s duty to control crime,” Gerstein v. Pugh, 420 U.S.
103, 112 (1975), “safeguard[ing] citizens from rash and
unreasonable interferences with privacy” while conferring
commonsense flexibility to police officers, Brinegar, 338
24 UNITED STATES V. ESTRELLA

U.S. at 176. Comparatively, the government’s “objectively
reasonable belief” standard is amorphous, and could be
construed to require either “probable cause” or “reasonable
suspicion.” See, e.g., United States v. Gorman, 314 F.3d
1105, 1110–15 (9th Cir. 2002) (discussing confusion created
by the “reasonable belief” prerequisite for residential
searches, and ultimately equating this standard to probable
cause). Defining the requisite knowledge as probable cause
ameliorates this confusion.
The probable cause threshold also accords with our
caselaw defining the scope of a parole search. Before they
may search property pursuant to a parole condition
authorizing suspicionless searches, “officers must have a
sufficient ‘degree of knowledge’ that the search condition
applies to the place or object to be searched.” United States
v. Dixon, 984 F.3d 814, 821 (9th Cir. 2022) (quoting United
States v. Grandberry, 730 F.3d 968, 974 (9th Cir. 2013)).
Implementing this prerequisite, we have twice defined the
necessary “degree of knowledge” to be probable cause. See,
e.g., Dixon, 984 F.3d at 822 (addressing searches of
vehicles); Grandberry, 730 F.3d at 973 (addressing searches
of homes).12 These cases recognize that a probable cause
requirement provides ample protection for the interests of
third parties—and that a lesser standard would undermine
their most essential Fourth Amendment rights. Dixon, 984
F.3d at 822 (“[A] reasonable suspicion standard runs the risk
of officers conducting intrusive searches on vehicles that
have no connection to the individual subject to the search

12
Once they are inside a parolee’s residence, officers “need only
‘reasonable suspicion’ that an item is owned, possessed, or controlled by
the parolee.” United States v. Bolivar, 670 F.3d 1091, 1095 (9th Cir.
2012).
 UNITED STATES V. ESTRELLA 25

condition.”); Grandberry, 730 F.3d at 982 (“[R]equiring
officers to have probable cause to believe that a parolee
resides at a particular address prior to conducting a parole
search protects the interest of third parties.” (quoting Motley,
432 F.3d at 1080)). Here, too, the principled rules governing
probable cause are better aligned to protect third parties
against unjustified assumptions about their parole status.
Estrella counters that the public policy and privacy
interests at stake compel a more rigid standard, and that
anything short of actual knowledge is insufficient to justify
the gravity of the intrusions authorized by this statute.13 As
Estrella notes:

Officer Trouette’s experience with the
general length of parole cannot make up for
his ignorance about Mr. Estrella’s particular
parole term. It is unreasonable for an officer
to believe that every parole term is at least
three years based on the usual term being
three to four years. Otherwise, police officers
could stop and search everyone released on
parole for at least three years after release
without ever checking the length of their
parole.

However, this argument dilutes the record. Trouette did not
merely assume that Estrella had an average parole term—he

13
Estrella also notes that increased police discretion to perform stops of
this nature could contribute to racial profiling. However, Estrella’s
framework does little to guard against this possibility. Even if officers
were required to verify a parolee’s status before conducting a routine
compliance check, that discretion could be abused in the manner he
describes.
26 UNITED STATES V. ESTRELLA

spoke with Estrella personally, maintained communication
with the defendant’s parole officer, reviewed his parole
conditions, and received information that he had violated his
parole only four months prior. A suspicionless search or
seizure based on broad generalizations about the defendant
or his expected length of parole, with little to no
particularized knowledge about the defendant’s case, would
almost certainly be unreasonable. But that would be a
different case.
***
Applying the foregoing principles, we hold that a law
enforcement officer must have probable cause to believe that
an individual is on active parole before conducting a
suspicionless search or seizure pursuant to a parole
condition. Consistent with our caselaw, and with general
Fourth Amendment principles, the officer must possess
advance knowledge of an applicable parole condition before
they may detain or search a parolee. Moreno, 431 F.3d at
641. That knowledge must be particularized enough for the
officer to be aware that a parole condition applies and
authorizes the encounter. Caseres, 533 F.3d at 1076.
However, the officer need not be absolutely certain, with
ongoing day-by-day or minute-by-minute awareness of the
subject’s parole status. Douglas, 193 Cal. Rptr. 3d at 89–
90.14 Instead, it is sufficient for the officer to find, using the
well-established rules governing probable cause, that the

14
We further note that existing rules governing staleness of probable
cause may be applied by analogy to determine exactly when it is
unreasonable for an officer to proceed without updating their
information. Cf. United States v. Ped, 943 F.3d 427, 432 (9th Cir. 2019)
(applying staleness principles to determine whether officers had
probable cause to search residence for parolee).
 UNITED STATES V. ESTRELLA 27

individual to be searched is on active parole, and an
applicable parole condition authorizes the search or seizure
at issue.
Applying this rubric, we hold that Trouette had probable
cause to believe that Estrella was on active parole at the time
of the encounter. As in Douglas, Trouette was familiar with
Estrella: He met Estrella personally, reviewed his criminal
history, discussed his parole conditions, and maintained
contact with his parole officer. Although he did not know the
precise start and end dates of Estrella’s parole term, he knew
that California parole ordinarily lasts three to four years. He
also had good reason to believe that Estrella’s term was not
over: Estrella was released from prison in July 2018, about
one year prior, and had violated a parole condition in April
2019, only four months prior. And distinct from Caseres,
there was no uncertainty that Estrella was placed on
California parole. Accordingly, Trouette had probable cause
to believe that Estrella was subject to the statutory search
condition imposed by Cal. Penal Code § 3067(b)(3), even
without “up-to-the-minute” confirmation of his parole
status. Cf. Douglas, 193 Cal. Rptr. 3d at 89.
II. Prohibition on Arbitrary and Harassing Searches
In the alternative, Estrella argues that the entire
encounter was arbitrary, as Trouette was motivated to train
Cooley, rather than to perform legitimate police duties. A
parole search may be unconstitutional if “the officers
violated California’s prohibition against arbitrary,
capricious, or harassing searches.” Cervantes, 859 F.3d at
1183; accord Samson, 547 U.S. at 856; Ped, 943 F.3d at 432.
Under California law, a search constitutes harassment if it is
“unrelated to rehabilitative, reformative or legitimate law
enforcement purposes, or when the search is motivated by
28 UNITED STATES V. ESTRELLA

personal animosity toward the parolee.” People v. Reyes,
968 P.2d 445, 451 (Cal. 1998) (quoting In re Anthony S, 6
Cal. Rptr. 2d 214, 217 (1992)). This prohibition is decidedly
narrow: “It is only when the motivation for the search is
wholly arbitrary, when it is based merely on a whim or
caprice or when there is no reasonable claim of a legitimate
law enforcement purpose . . . that a search based on a
probation search condition is unlawful.” People v.
Cervantes, 103 Cal. App. 4th 1404, 1408 (Cal. Ct. App.
2002), as modified (Dec. 23, 2002).15
Estrella argues that “Officer Trouette treated the
interaction with Mr. Estrella as a ‘training tool’ for Officer
Cooley,” and that the officers had no legitimate reason to
detain him.16 Trouette was responsible for training Cooley
as part of the LPD’s field training program. Additionally, he
attested that he perceived the stop as a training opportunity,
and withheld information from Cooley to test the junior
officer’s resourcefulness. Estrella contends that this is not a

15
For example, “a parole search could become constitutionally
‘unreasonable’ if made too often, or at an unreasonable hour, or if
unreasonably prolonged or for other reasons establishing arbitrary or
oppressive conduct by the searching officer.” Reyes, 968 P.2d at 451
(quoting People v. Clower, 21 Cal. Rptr. 2d 38, 41 (Cal. Ct. App. 1998)).
16
In making this argument, Estrella insists that “[t]he only legitimate law
enforcement purposes” that justify a suspicionless parole search “are
‘reducing recidivism’ and ‘promoting reintegration and positive
citizenship,’” Samson, 547 U.S. at 854, and argues that officers “abuse
their discretion” by acting outside these purposes. This argument
conflates the policy rationale articulated in Samson with the Court’s
holding. Cal. Penal Code § 3067 authorizes suspicionless parole searches
for any legitimate law enforcement purpose, provided that objective is
not arbitrary, capricious, or harassing. Samson, 547 U.S. at 856. It is not
limited to “reducing recidivism” and “promoting reintegration and
positive citizenship,” and we decline to constrain it in this manner.
 UNITED STATES V. ESTRELLA 29

legitimate purpose for a parole search, and that his search
and seizure were arbitrary and capricious. Cf. Cervantes, 103
Cal. App. 4th at 1408 (“A search is a form of harassment
when its motivation is a mere whim or caprice . . . e.g., an
officer decides on a whim to stop the next red car he or she
sees.”).
We need not decide whether a stop undertaken solely to
train a junior officer would be arbitrary or capricious,
because the record does not support Estrella’s claim that the
officers searched and seized him exclusively as a training
exercise. Rather, Trouette decided to conduct a parole
compliance check and saw Estrella wearing an Oakland
Athletics hat—a symbol of the Angelino Heights Sureños
and a violation of Estrella’s parole conditions. This is a
wholly legitimate reason to conduct a parole or probation
search under California law. See, e.g., People v. Woods, 981
P.2d 1019, 1027–28 (Cal. 1999) (noting that probation
searches may be conducted to “monitor the probationer”). It
is true that Trouette brought Cooley into the field to train him
in the fundamentals of police work, and it may be true that
he saw the encounter with Estrella as an opportunity to
provide such instruction. Regardless, these considerations
do not vitiate Trouette’s legitimate reason for initiating the
encounter. The entire point of field training programs is to
give new officers experience with police work through
hands-on encounters in the field. That does not make them
harassment.
CONCLUSION
For the reasons set forth above, we AFFIRM the denial
of Estrella’s motion to suppress.