                   Corrected Reprint 3/19/07

                     FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                         No. 05-30347
                Plaintiff-Appellee,
               v.                                   D.C. No.
                                                   CR-04-114-KI
HOSVALDO LOPEZ,
                                                    OPINION
            Defendant-Appellant.
                                           
         Appeal from the United States District Court
                  for the District of Oregon
           Garr M. King, District Judge, Presiding

                    Argued and Submitted
                May 5, 2006—Portland, Oregon

                       Filed March 12, 2007

      Before: William A. Fletcher, and John T. Noonan,
     Circuit Judges, and Louis H. Pollak,* District Judge.

                   Opinion by Judge Pollak;
                 Concurrence by Judge Noonan




  *Honorable Louis H. Pollak, United States District Court Judge for the
Eastern District of Pennsylvania, sitting by designation.

                                 2913
                    UNITED STATES v. LOPEZ                2917


                         COUNSEL

Bryan E. Lessley, Office of the Federal Public Defender,
Eugene, Oregon, for the appellant.

Charles W. Stuckey (argued) and Karin J. Immergut, Office
of the United States Attorney, Portland, Oregon, for the appel-
lee.


                         OPINION

POLLAK, District Judge:

  In February 2005, the District Court of Oregon denied
defendant Hosvaldo Lopez’s pretrial motion to suppress evi-
dence found in his car. Lopez subsequently pled guilty to pos-
sessing methamphetamine with intent to distribute in violation
of 21 U.S.C. § 841(a), but reserved the right to appeal the
denial of his motion to suppress. He was sentenced to a term
2918                    UNITED STATES v. LOPEZ
of incarceration of 135 months. He now timely appeals from
the denial of his pretrial motion to suppress evidence and his
resulting conviction. Because we conclude that the police had
probable cause to arrest Lopez as an accessory to another
crime, and, while in custody, Lopez voluntarily consented to
a search of his car, we affirm the District Court’s denial of the
motion to suppress and the resulting conviction and sentence.

                                     I.

   At a quarter past noon on March 4, 2004, while two law
enforcement officers—members of the West Side Interagency
Narcotics Team—were interviewing a witness in a narcotics
investigation in the front yard of a residence in Hillsboro,
Washington County, Oregon, a man drove up, got out of his
car and began to approach the group. The witness, however,
motioned the man away, and when one of the officers called
the man back, the man turned and drew a gun on the officers.
According to the officers, the man appeared to try to fire the
weapon but then returned to his car—a green Ford Focus—
and sped away.

   Based on the two officers’ description of the suspect, an
alert was immediately issued for police to look for “an adult,
male Hispanic in his 20s, thin build, taller, wearing a white
sweater, and armed with a firearm.”1 An accurate description
of the attempted shooter’s getaway car—including its make,
model, and license plate number—was also provided.

  At approximately a quarter to one in the afternoon—about
half an hour after the front-yard encounter—the Ford Focus
  1
   At the suppression hearing, Detective Stephen Schuster first character-
ized the description received by the police as “Hispanic male, adult,
approximately 20 years old with short black hair, thin build, taller,” and
then, later in his testimony, as an “Hispanic male adult, approximately 20
years of age, tall, thin.” Detective Schuster was relying on his memory, as
he had not recorded the full description in his report, and he stated that he
did not “recall as far as the exact description.”
                        UNITED STATES v. LOPEZ                        2919
was found nearby, in the parking lot of a Fred Meyer store.2
Based on the license plate number, the police secured the
name of the registered owner—Roberto Lopez Gamez—and
his physical description, which included Gamez’s height and
weight, from the Department of Motor Vehicles.3

   The police staked out the area. About eight hours later,
their vigilance was rewarded. Officers observed a white,
1990s Ford Taurus with tinted windows enter the parking lot
and park near the Ford Focus. A female passenger, later iden-
tified as Alicia Polish, got out of the Ford Taurus, got into the
Ford Focus, started it, and drove off, leaving through the west
exit of the parking lot and entering the adjoining road. The
Ford Taurus also departed; the driver was observed to be a
Hispanic male, approximately twenty years old. Although the
Ford Taurus left the parking lot through the southeast exit, it
then turned onto the road on which the Ford Focus was travel-
ing and proceeded to follow the Ford Focus at a distance of
approximately four hundred yards.

   Officers stopped both cars, using a “high risk traffic stop”
technique involving multiple police cars, officers, and the
pointing of firearms. The driver of the Ford Taurus was
ordered out of the car at gunpoint, while surrounded by sev-
eral police cars and officers. He was told to lie on the ground
and was placed in handcuffs. Next, he was patted down for
weapons; none were found. The police located his wallet and
  2
     Fred Meyer is a Northwestern chain of large, “multi-department stores”
retailing groceries, apparel, and other goods. See Cliff Peale, For Kroger,
Fred Meyer Is the Future: Customers Loyal to Northwest Store, Cincinnati
Post (Ky.), Nov. 16, 1998, at 1A (describing merger of Fred Meyer and
Kroger Co.).
   3
     The Department of Motor Vehicles’ file for Gamez also included a
photograph. The record does not make clear when that photograph was
made available to police. At the suppression hearing, Detective Schuster
initially testified that a photograph of Gamez was brought to the scene, but
he then revised his testimony, stating that he could not recall with cer-
tainty when the photograph became available.
2920                    UNITED STATES v. LOPEZ
found a driver’s license in the name of Hosvaldo Lopez, the
defendant-appellant in this action. Lopez was then detained
inside one of the patrol cars. The government alleges, and
Lopez does not deny, that, during this process, he twice ver-
bally consented to a search of his car (although the police did
not, at that time, conduct such a search). Shortly thereafter, he
was asked to accompany police officers to the Hillsboro
Police Department.4 Lopez was transported to the station in
the back of a patrol car and, upon arrival, was placed in the
custody of detectives. According to police testimony, Lopez
was fully cooperative and compliant throughout.

   At the station, Lopez was advised, in Spanish, of his rights
under Miranda v. Arizona, 384 U.S. 436 (1966), and his right
to refuse to consent to a search of his Ford Taurus. Following
questioning, he was asked to provide written consent to a
search of his vehicle, which he did. During their subsequent
search, police found a secret compartment behind the back
seat of the car, which contained illicit drugs, cash, and a
loaded firearm.

  It was ultimately determined that the alleged attempted
shooter—the suspect sought on March 4, 2004—was Roberto
Lopez Gamez, the registered owner of the Ford Focus, and
not appellant Hosvaldo Lopez.
  4
    According to testimony of police officers, although Lopez was nomi-
nally “asked” to accompany the police to the station (rather than continue
to be questioned on the side of the road), he was not told that he was free
to leave, and indeed the officers did not consider him free to leave.
   The government states that the request to move Lopez to the station was
based both on the desire of officers to ask further questions and on con-
cerns about the safety of interviewing him on the side of the road. The tes-
timony of the officers makes clear that the primary motive for relocating
Lopez was to allow investigators at the station to speak with him. Some
officers stayed on the roadside with the Ford Taurus for several hours and,
at approximately eleven o’clock, conducted a search of the vehicle (the
search which has been put in issue by Lopez’s motion to suppress) without
removing the vehicle from that location.
                        UNITED STATES v. LOPEZ                       2921
                                   II.

   Lopez’s pretrial motion to suppress argued that, under the
Fourth and Fifth Amendments, his stop, detention, and ensu-
ing custody constituted an illegal seizure and that any state-
ments or other evidence obtained from him or from his
vehicle must be excluded as fruits of that illegality, or as evi-
dence derivative therefrom. The District Court denied Lopez’s
motion, holding that (a) the officers had the reasonable suspi-
cion required for an investigative Terry stop (see Terry v.
Ohio, 392 U.S. 1 (1968)), and (b), given that Lopez “substan-
tially fit the description of the suspect,” “the arresting officers
had probable cause to take defendant into custody.” The Dis-
trict Court also found that, at the police station, Lopez validly
waived his Miranda rights and voluntarily consented to the
search of his car.

   On appeal, Lopez concedes that the police possessed rea-
sonable suspicion to stop his car, but he maintains that the
police lacked probable cause to arrest him and that evidence
obtained as a result of that arrest must be suppressed. The
government maintains that the arrest was supported by proba-
ble cause. According to the government, “[i]t was reasonable
to believe that the defendant was either the person involved
in the earlier attempted shooting of the police officers or that
he was an accessory after the fact, in violation of 18 U.S.C.
§ 3.”5
  5
   In the alternative, the government argues that probable cause was not
needed because Lopez’s detention was not an arrest, but a valid Terry
stop, and, therefore, the evidence recovered from Lopez’s car was not
obtained in violation of the Constitution, because Lopez “agreed to the
search . . . voluntarily” while “in investigatory detention.” Because we
find that the police had probable cause for an arrest, see infra Part IV.C,
we need not address this alternative argument.
2922                UNITED STATES v. LOPEZ
                              III.

   “In general, we review determinations of motions to sup-
press de novo.” United States v. Becker, 23 F.3d 1537, 1539
(9th Cir. 1994) (citing United States v. Khan, 993 F.2d 1368,
1375 (9th Cir. 1993)). This court reviews de novo whether
probable cause to arrest Lopez existed, as the question raises
mixed questions of law and fact. See Ornelas v. United States,
517 U.S. 690, 699 (1996); United States v. Carranza, 289
F.3d 634, 640 (9th Cir. 2002).

  “We may affirm a district court’s denial of a motion to sup-
press on any basis supported in the record.” United States v.
Ruiz, 428 F.3d 877, 880 (9th Cir. 2005); United States v.
Albers, 136 F.3d 670, 672 (9th Cir. 1998).

                              IV.

   In our view, the central questions to be addressed in deter-
mining whether Lopez’s motion to suppress was properly
denied are whether, at the time Lopez, at the police station,
consented to the search of his car, (a) he was under arrest, (b)
there had been probable cause for that arrest, and (c) probable
cause had not been dissipated. Because our answers to the lat-
ter two questions are dispositive of this appeal, we do not
answer the first question, but rather assume without deciding
that the District Court was correct in finding that the investi-
gative stop of Lopez’s vehicle promptly escalated into what,
“for Fourth Amendment purposes,” constituted a “full-scale
arrest” of Lopez.

   In the balance of this opinion, we start by examining what
constitutes probable cause. We then address the two theories
of probable cause for Lopez’s arrest advanced by the govern-
ment. We find that the government’s first theory, while ini-
tially adequate to support Lopez’s arrest, was no longer viable
by the time Lopez consented to the search of his car, since by
then the police had acquired additional information that
                     UNITED STATES v. LOPEZ                  2923
undercut probable cause. But we further find that the govern-
ment’s second probable cause theory not only validates
Lopez’s arrest, but remains supportive of Lopez’s continuing
arrest status at the time of his consent to the search of his car.
Because we find that there was probable cause to arrest
Lopez, and that the probable cause was still in force at the
time Lopez consented to the search, we hold that the District
Court properly denied the motion to suppress.

A.   The probable cause standard

   [1] Under the Fourth Amendment, a warrantless arrest
requires probable cause. See Michigan v. Summers, 452 U.S.
692, 700 (1981). Probable cause to arrest exists when officers
have knowledge or reasonably trustworthy information suffi-
cient to lead a person of reasonable caution to believe that an
offense has been or is being committed by the person being
arrested. Beck v. Ohio, 379 U.S. 89, 91 (1964). Alternatively,
this court has defined probable cause as follows: when “under
the totality of circumstances known to the arresting officers,
a prudent person would have concluded that there was a fair
probability that [the defendant] had committed a crime.”
United States v. Smith, 790 F.2d 789, 792 (9th Cir. 1986).
While conclusive evidence of guilt is of course not necessary
under this standard to establish probable cause, “[m]ere suspi-
cion, common rumor, or even strong reason to suspect are not
enough.” McKenzie v. Lamb, 738 F.2d 1005, 1008 (9th Cir.
1984) (citing Henry v. United States, 361 U.S. 98, 101
(1959)).

   [2] Probable cause is an objective standard. The arresting
officers’ subjective intention (i.e., in this case, the crime for
which they thought they were arresting Lopez) is immaterial
in judging whether their actions were reasonable for Fourth
Amendment purposes. See Devenpeck v. Alford, 543 U.S.
146, 153 (2004) (“Our cases make clear that an arresting offi-
cer’s state of mind (except for the facts that he knows) is irrel-
evant to the existence of probable cause . . . . [H]is subjective
2924                   UNITED STATES v. LOPEZ
reason for making the arrest need not be the criminal offense
as to which the known facts provide probable cause.” (cita-
tions omitted)); Whren v. United States, 517 U.S. 806, 814
(1996). Generally, “an officer need not have probable cause
for every element of the offense.” Gasho v. United States, 39
F.3d 1420, 1428 (9th Cir. 1994). However, as will be relevant
to our discussion below, see infra Part IV.C, “when specific
intent is a required element of the offense, the arresting offi-
cer must have probable cause for that element in order to rea-
sonably believe that a crime has occurred.” Id.6

   In some instances there may initially be probable cause jus-
tifying an arrest, but additional information obtained at the
scene may indicate that there is less than a fair probability that
the defendant has committed or is committing a crime. In
such cases, execution of the arrest or continuation of the arrest
is illegal. As we explained in United States v. Ortiz-
Hernandez, 427 F.3d 567, 574 (9th Cir. 2005), cert. denied,
127 S. Ct. 358 (2006):

      A person may not be arrested, or must be released
      from arrest, if previously established probable cause
      has dissipated. “As a corollary . . . of the rule that the
      police may rely on the totality of facts available to
      them in establishing probable cause, they also may
      not disregard facts tending to dissipate probable
      cause.” Bigford v. Taylor, 834 F.2d 1213, 1218 (5th
      Cir. 1988); BeVier v. Hucal, 806 F.2d 123, 128 (7th
      Cir. 1986) (citation omitted) (“The continuation of
      even a lawful arrest violates the Fourth Amendment
      when the police discover additional facts dissipating
      their earlier probable cause.”).
  6
   This requirement arises from the deeply-rooted precept “that a person
is not criminally responsible unless criminal intent accompanies the
wrongful act.” Gasho, 39 F.3d at 1429 (citing Morissette v. United States,
342 U.S. 246, 251 (1952)).
                    UNITED STATES v. LOPEZ                2925
   In light of Ortiz-Hernandez, the critical question before us
is whether the police had probable cause when they ques-
tioned Lopez at the police station and obtained written per-
mission to search his car. It will not suffice that, at some
earlier point in time—before the police gleaned certain “dissi-
pating” facts—the police may have had probable cause. The
question we must answer is: At the time that Lopez was
Mirandized and signed the written consent, did the totality of
the facts available to the police provide probable cause?

B.   Probable cause to arrest Lopez as principal

  The District Court was satisfied that there was probable
cause to hold Lopez under arrest for the attempted shooting,
given Lopez’s observed interaction with the green Ford Focus
and the fact that he “substantially fit the description of the
suspect.” We conclude, however, that when, subsequent to
Lopez’s having been brought to the police station, he was
asked to consent to the search of his car, the police lacked
probable cause to believe that Lopez was the attempted
shooter.

   [3] While Lopez matched the general description of the
suspect as a young Hispanic man, he did not fit the more spe-
cific aspects of the description—a description which had been
provided by two trained law enforcement officers and had
proved to be entirely accurate with respect to the getaway car.
Most notably, Lopez is rather short at 5′6″, while the suspect
was described as “taller” or “tall.” Lopez and the suspect also
differed with regard to several mutable—and hence less
consequential—characteristics or features: The suspect had a
gun, but Lopez was found to be unarmed. The suspect did not
wear eyeglasses, but Lopez was wearing prescription glasses.
And the suspect was described as wearing a sweater, but
Lopez, when apprehended, was not wearing a sweater.

  [4] “Under the law of this Circuit, mere resemblance to a
general description is not enough to establish probable cause.”
2926                UNITED STATES v. LOPEZ
Grant v. City of Long Beach, 315 F.3d 1081, 1088 (9th Cir.
2002); see, e.g., United States v. Ricardo D., 912 F.2d 337,
342 (9th Cir. 1990) (finding that officers did not have proba-
ble cause to arrest suspect merely because he appeared to
match separate reports describing a “ ‘young, thin man, not
too tall’ ” and a “ ‘young, Mexican male’ ”); see also United
States v. Montero-Camargo, 208 F.3d 1122, 1132, 1134 n.22
(9th Cir. 2000) (en banc) (noting that racial or ethnic charac-
teristics alone are insufficient to establish reasonable suspi-
cion, and holding that, where no particularized suspicion
exists, racial resemblance is not relevant or appropriate to the
reasonable suspicion analysis). However, it is permissible to
consider a general physical description where it is found in
combination with other particularized bases for suspicion. See
Montero-Camargo, 208 F.3d at 1134 n.21; United States v.
Bautista, 684 F.2d 1286, 1289 (9th Cir. 1982) (holding that
racial appearance may be relevant where there are other fac-
tors creating suspicion).

   [5] In this case, Lopez’s resemblance to the suspect in
terms of age, gender, and ethnicity had some, albeit modest,
probative weight; however this modest weight was itself
undercut by disparities which suggested that Lopez was not
the sought-after suspect. Indeed, the government’s brief states
that “the critical factor giving rise to probable cause was not
the general description of the suspect, but the connection
between the defendant and the suspect car, the green Ford
Focus.”

   [6] The government’s analysis, however, overstates the sig-
nificance of Lopez’s connection to the getaway car, insofar as
it is contended that the connection shows Lopez was the
attempted shooter. But cf. infra Part IV.C. And, more impor-
tantly, the government’s analysis fails to account for substan-
tial, countering indicators. The effect of evidence which may
support, or incline toward, a finding of probable cause can, of
course, be vitiated by countervailing evidence. See Ortiz-
Hernandez, 427 F.3d at 574. This was the case here, where
                     UNITED STATES v. LOPEZ                    2927
there was substantial evidence known to the police tending to
show that the defendant was not the person responsible for the
earlier attempted shooting.

   It is well established that a person’s mere presence or
“mere propinquity to . . . criminal activity does not, without
more, give rise to probable cause.” Ybarra v. Illinois, 444
U.S. 85, 91 (1979) (holding that police lacked probable cause
to search a person based solely on his presence in a tavern at
a time when the police had reason to believe the bartender
possessed heroin for sale). We have distinguished the “mere
presence” doctrine from cases in which the “facts and circum-
stances . . . support an inference that [an] individual is con-
nected to the proximate criminal activity.” United States v.
Buckner, 179 F.3d 834, 839 (9th Cir. 1999). Although the
government argues that this is such a case, we find this case
distinguishable from Buckner and the other cases cited by the
government.

    In Buckner, we concluded that the “attendant facts and cir-
cumstances support[ed] a fair probability” that the defendant
—the sole passenger in a car carrying thirty-seven pounds of
marijuana hidden in the dashboard and rear panels—“was
linked to the crime of drug trafficking.” Id. We noted a num-
ber of relevant facts, including the following: the car belonged
to neither occupant and was procured under suspicious cir-
cumstances, the car was entering the United States from a
Mexican city known as a drug source, and officers considered
it typical for drug traffickers to travel in pairs to deflect suspi-
cion. Id. at 837, 839; see also Carranza, 289 F.3d at 640
(finding probable cause where inspectors knew that defendant
was sole passenger in vehicle carrying commercial quantity of
illegal drugs across the border; there was strong smell of gas-
oline coming from the vehicle, and gas tanks are frequently
used to smuggle drugs; and driver of the vehicle made suspi-
cious, false statements); United States v. Valencia-Amezcua,
278 F.3d 901, 906-08 (9th Cir. 2002) (finding probable cause
based on defendant’s physical proximity to the crime scene
2928                    UNITED STATES v. LOPEZ
and suspicious conduct in helping to attempt to conceal a
secret door).

   [7] The instant case is unlike Buckner, Carranza, and
Valencia-Amezcua in several respects. To begin, Lopez was
not directly or immediately associated with the scene of the
crime (the attempted shooting). The public parking lot to
which he delivered Ms. Polish (approximately eight hours
after the incident involving the Ford Focus driver and the law
enforcement officers) was at least some distance away from
the crime scene, and Lopez did not make direct contact with
the getaway vehicle—Polish was the one to take possession
of the Ford Focus. In Buckner and Carranza, by comparison,
the arrested person was present in a car when it was found to
be transporting illegal drugs—providing both temporal and
physical proximity to the commission of a crime. See Buck-
ner, 179 F.3d at 838; Carranza, 289 F.3d at 637-39; see also
Valencia-Amezcua, 278 F.3d at 907-08 (noting defendant’s
physical and temporal proximity to the crime scene).

   [8] Moreover, we find that attendant facts gathered by the
police tended to dissipate, rather than support, probable cause
to believe Lopez was the attempted shooter.7 After he was
stopped, Lopez was positively identified as Hosvaldo Lopez,
the registered owner of the Ford Taurus he was driving. When
the police removed Lopez’s driver’s license from his wallet,
they could readily compare it with the information they had
from the Department of Motor Vehicles regarding the owner
of the Ford Focus and see that Lopez and Gamez had different
names. The police were also in a position to observe that
Lopez’s appearance did not match the Department of Motor
Vehicles’ physical description of Gamez.8 It should then have
   7
     The only attendant fact highlighted by the District Court as contribut-
ing to its probable cause determination was Lopez’s general resemblance,
as a young Hispanic male, to the suspect—discussed supra. There is no
indication in the record that the police found other features, such as his
car’s tinted windows, to be problematic.
   8
     The record does not include the full contents of the DMV information
for Gamez. However, Detective Schuster testified that the police had this
                        UNITED STATES v. LOPEZ                       2929
been manifest that Lopez was not Gamez, the registered
owner of the getaway car. Furthermore, police officers testi-
fied that “Lopez was actually very cooperative” and
responded appropriately and “without hesitation” to all of the
officers’ requests. Cf. United States v. Mills, 280 F.3d 915,
921 (9th Cir. 2002) (finding that defendant’s suspicious
remarks to the police were a factor supporting probable
cause).

   [9] By the time Lopez was brought to the police station for
questioning and to give consent to the search of his car, the
police had observed and gathered a substantial amount of
information. Given the totality of the facts the police had
assembled by the time they commenced questioning Lopez at
the police station, we conclude that the police did not then
have probable cause to believe that Lopez was the attempted
shooter.

C.   Probable cause to arrest Lopez as accessory

   Our conclusion that, at the time Lopez was questioned at
the police station, the police did not have probable cause to
regard Lopez as the attempted shooter does not, however, end
our inquiry. The government’s brief on appeal suggests that,
even if there was an insufficient basis from which to infer that
Lopez was the person responsible for the earlier attempted
shooting, there was still probable cause to arrest him as an
accessory after the fact under 18 U.S.C. § 3. This basis for
probable cause was not argued to the District Court, nor was
its Oregon state law counterpart, Or. Rev. Stat. § 162.325
(2003) (“Hindering prosecution”). However, as noted above,
we can affirm on any basis evident in the record. Ruiz, 428
F.3d at 880.

information, and that it matched or was “similar” to the eyewitness
description of the attempted-shooting suspect as “taller” or “tall.” Detec-
tive Schuster also testified that he would not describe Lopez, who “was
5′6″ based on his DMV information,” as “taller.”
2930                     UNITED STATES v. LOPEZ
   [10] Under 18 U.S.C. § 3, “Whoever, knowing that an
offense against the United States has been committed,
receives, relieves, comforts or assists the offender in order to
hinder or prevent his apprehension, trial or punishment, is an
accessory after the fact.” 18 U.S.C. § 3. In addition to the
actus reus of receiving, relieving, comforting or assisting the
offender, we have interpreted this statutory language to
require (1) specific intent to frustrate law enforcement, see
United States v. Hill, 279 F.3d 731, 737 (9th Cir. 2002); (2)
“commission of the underlying offense” by the principal, see
United States v. Innie, 7 F.3d 840, 850 (9th Cir. 1993); and
(3) actual, specific knowledge of the underlying crime on the
part of the accessory, see United States v. Graves, 143 F.3d
1185, 1190 (9th Cir. 1998) (as amended); cf. United States v.
Burnette, 698 F.2d 1038, 1051 (9th Cir. 1983) (noting that
such knowledge “may be shown entirely through circumstan-
tial evidence”).

   [11] The elements of the analogous Oregon crime of hin-
dering prosecution are essentially the same—the commission
of the underlying crime, acts aiding the perpetrator of that
crime in escaping justice, and the intent to frustrate law
enforcement—with the important exception that knowledge of
the underlying crime is not required. See Or. Rev. Stat.
§ 162.325;9 State v. Allred, 995 P.2d 1210, 1213-14 (Or. Ct.
App. 2000) (noting 1971 legislative amendment “deleting the
  9
   A person commits the crime of hindering prosecution if,
      with intent to hinder the apprehension, prosecution, conviction or
      punishment of a person who has committed a crime punishable
      as a felony . . . the person: . . .
      (c) Provides or aids in providing such person with money,
      transportation, weapon, disguise or other means of avoiding dis-
      covery or apprehension; or . . .
      (e) Suppresses by any act of concealment, alteration or destruc-
      tion physical evidence which might aid in the discovery or appre-
      hension of such person . . . .
Or. Rev. Stat. § 162.325(1).
                        UNITED STATES v. LOPEZ                         2931
requirement that a defendant know that the person he or she
aided in fact had committed a felony”).

   [12] The extent to which Lopez fit the general physical
description of the attempted shooter is obviously not relevant
to an assessment of probable cause to arrest as an accessory
under 18 U.S.C. § 3 or Or. Rev. Stat. § 162.325. The relevant
inquiry is whether the police had information that would rea-
sonably lead to the conclusion, by a fair probability, that
Lopez knew that the attempted shooter had committed an
offense against the United States10 (or, as to Oregon law, that
the attempted shooter was being sought by law enforcement),
and that Lopez was acting to assist the attempted shooter in
order to hinder or prevent his apprehension. We undertake
this inquiry based on the totality of the circumstances. See
supra Part IV.A. However, because 18 U.S.C. § 3 and Or.
Rev. Stat. § 162.325 define specific-intent crimes, we are also
called upon to determine whether the police had probable
cause to believe Lopez was acting with the specific intent to
frustrate law enforcement. See supra Part IV.A (citing Gasho,
39 F.3d at 1428).

  [13] Although we find a dearth of specifically applicable pre-
cedent,11 we are satisfied that the facts known to the police in
  10
      The arresting officers were state officers. Our review of Oregon statu-
tory and case law leaves us unsure whether, in Oregon, state law enforce-
ment officers have authority to arrest for violations of federal law. Under
some circumstances this could be of import, because whether an arrest is
valid under state law can be relevant to deciding whether that arrest is
valid for Fourth Amendment purposes. See United States v. Miranda-
Guerena, 445 F.3d 1233, 1238 (9th Cir. 2006) (McKeown, J., concurring);
United States v. Cormier, 220 F.3d 1103, 1112 (9th Cir. 2000); United
States v. Mota, 982 F.2d 1384, 1387-89 (9th Cir. 1993). We need not
decide if such circumstances are present here, however, because we con-
clude that the officers had probable cause to believe Lopez had violated
not only federal law, but Oregon law as well. See text infra.
   11
      We do not find United States v. Hill, 279 F.3d 731 (9th Cir. 2002)—
the sole case cited by the government to support probable cause to arrest
2932                     UNITED STATES v. LOPEZ
this case provided probable cause under the standard dis-
cussed in Part IV.A and the previous paragraph. The Ford
Focus had been used as a getaway car,12 and presumably then
abandoned, by a man who tried to use a firearm in an attempt
to escape the scrutiny of narcotics investigators. The police
could reasonably infer that this man, who was apparently
ready to gun down a law enforcement officer, was involved
in additional criminal activity—specifically, narcotics activity
—and that he was also likely to have criminal associates. It
was also logical to assume that the attempted shooter would
be afraid to return and retrieve the car himself, and, moreover,
that he might turn to a trusted associate for help. The back-
ground facts available to the police thus supported the infer-
ence of a fair probability that Lopez knew the Ford Focus was
connected to a federal or Oregon crime.

Lopez as an accessory—to be helpful. The Hill court, in the course of
weighing a privacy-based, constitutional claim (not a Fourth Amendment
issue), found that the defendant had “self-evidently intended” to frustrate
law enforcement where she had “attempted to orchestrate . . . delivery” of
possessions to her husband—while also providing him with “shelter,
employment, money, food and other material support.” Id. at 737. The
government seeks to draw a parallel between these facts and Lopez’s
alleged attempt to “orchestrate . . . delivery” of the attempted shooter’s
car. As we have just noted, however, Hill listed an attempt to deliver pos-
sessions to a fugitive as a cumulative fact pointing to accessory liability
in a case involving extensive additional evidence. Hill illustrates that pick-
ing up or taking possession of a fugitive’s possessions can—under some
circumstances—constitute evidence that one is acting as an accessory to
that fugitive’s crime. But because the scope and content of the assistance
rendered by the defendant to the fugitive was much broader and better
developed in Hill than in the case before us, Hill provides little help in
deciding whether Lopez’s actions in helping to recover the Ford Focus—
presented in the much sparser evidentiary context of our case—were suffi-
cient to justify arrest in what, we find, is “a close case.” Cf. Hill, 279 F.3d
at 737 (noting that “this is not a close case” as to criminal intent).
   12
      In Oregon, a getaway car is considered an instrumentality of the
crime. See State v. Walden, 515 P.2d 407, 409 (Or. Ct. App. 1973); State
v. Keith, 465 P.2d 724, 726 (Or. Ct. App. 1970).
                        UNITED STATES v. LOPEZ                        2933
   Set against this background, Lopez’s actions in helping to
rescue the Ford Focus provided further reason to believe that
he was acting to assist the attempted shooter and to hinder the
latter’s apprehension and prosecution. Lopez arrived at the
Fred Meyer parking lot and drove directly to the Focus. He
dropped off an associate who had the keys to the Ford Focus
—suggesting a personal link to the car’s earlier driver, the
attempted shooter. As Lopez’s associate departed from the
parking lot’s west exit in the Ford Focus, Lopez guided his
Ford Taurus out of the lot through the southeast exit—but
soon doubled back and rejoined the Ford Focus, trailing about
four hundred yards behind while traveling in the same direc-
tion.

   Even in the face of this suspicious behavior, there is, of
course, a possibility that Lopez was an unwitting acquaint-
ance of Ms. Polish’s, who simply drove her to the parking lot,
with no guilty knowledge or illicit motive. However, the
police were not required to believe to an absolute certainty, or
by clear and convincing evidence, or even by a preponderance
of the available evidence, that Lopez had committed a crime
—what was required was a fair probability, given the totality
of the circumstances. The police had good reason to suspect
that a criminal enterprise (the recovery of the Ford Focus,
with the intent to impede the identification of the vehicle’s
owner, the attempted shooter) was afoot, and that Lopez was
playing a key role in that enterprise. Lopez was connected to
the Ford Focus—an instrumentality of the underlying crime—
and he appeared to be taking steps to avoid detection. Upon
being stopped, Lopez apparently offered no explanation for
his actions.13 A plausible, innocent explanation for his conduct
  13
    Apart from disclosing one’s identity, see Hiibel v. Sixth Judicial Dist.
Court of Nev., 542 U.S. 177, 187-89 (2004), a person detained by police
has no general obligation to answer questions or volunteer information.
See, e.g., Davis v. Mississippi, 394 U.S. 721, 727 n.6 (1969); Graves v.
City of Coeur D’Alene, 339 F.3d 828, 842 n.18 (9th Cir. 2003), abrogated
in part by Hiibel, 542 U.S. 177.
2934                UNITED STATES v. LOPEZ
might have dissipated the effect of the incriminating facts
canvassed above; without such an explanation, Lopez’s con-
nection to the Ford Focus might well have seemed to a rea-
sonable police officer to be of real significance.

   [14] We think that Lopez’s role in bringing a driver to res-
cue the Ford Focus, taken in conjunction with his apparent
effort to follow the Ford Focus out of the parking lot, could
properly have been perceived by a police officer as suspicious
activity. While not of overwhelming evidentiary weight, this
activity could have been regarded by a reasonable police offi-
cer as grounding an inference that Lopez was assisting a fed-
eral offender—the attempted shooter—with the intent to
hinder or prevent his apprehension. We therefore find that the
police had probable cause to believe Lopez was an accessory
after the fact, under 18 U.S.C. § 3, to the attempted shooter’s
crime, and that the police did not act unreasonably in holding
him under arrest without a warrant while they investigated
further. Since Oregon’s “hindering prosecution” statute does
not require as extensive a showing as its federal counterpart,
see supra text at note 10, our finding of probable cause under
18 U.S.C. § 3 applies a fortiori to Or. Rev. Stat. § 162.325.

D.     The motion to suppress

   [15] We have concluded that the knowledge and informa-
tion available to the police would have led a reasonable offi-
cer to believe that there was a fair probability that Lopez was
an accessory to a crime committed in the course of the
attempted shooting. The police gathered no information tend-
ing to dissipate that inference prior to the point at which
Lopez consented to the search of his car. Accordingly, we
find that, at the point when Lopez signed the consent to
search, the police validly held Lopez under arrest pursuant to
probable cause. Because the arrest was justified by probable
cause, and the consent to search was voluntary, the District
Court correctly denied the motion to suppress.
                    UNITED STATES v. LOPEZ                2935
                              V.

   Accordingly, we AFFIRM the decision of the District
Court denying Lopez’s motion to suppress, and we AFFIRM
the resulting judgment of conviction and sentence.

  AFFIRMED.



NOONAN, Circuit Judge, concurring in the judgment:

   What the police knew was that Lopez was not the regis-
tered owner of the Ford Focus whose rescue he had aided and
whose driver he had then taken steps to follow. What would
these facts suggest to a reasonable police officer? The police
knew that the gunman had engaged in a desperate enterprise
— an attempt to break up a police investigation by directing
deadly force at the police themselves. Would such a criminal
have used his own car? Not likely. That Lopez didn’t own the
Ford Focus didn’t help him a bit. In terms of diluting probable
cause it was a zero, just as his submissive behavior was a
zero.

   What might have dissipated probable cause was a plausible
explanation by Lopez of why he engaged in the rescue of the
Ford Focus. At the suppression hearing, he offered no less
than two accounts of why he dropped off the lady with the
keys to the Ford Focus and why he followed her out of the
parking lot. The record is barren of evidence that he offered
these explanations to the police at the time of his arrest.
Lopez’s failure to give an innocent connection with the car
must have loomed large in the mind of the police. Only an
unreasonably slack officer would have brushed off the con-
nection.

  That Lopez had no idea why he had been pursued from the
parking lot, surrounded by police cars, and at gun point
2936                UNITED STATES v. LOPEZ
ordered to the ground is unbelievable. Nothing suggests that
this drug dealer was a moron. He couldn’t figure out that his
part in rescuing the Ford Focus and following it in tandem
had made the police suspicious? It was his burden to show
that the police had been given a plausible story to account for
his extraordinary conduct. He had a fair amount of time to
converse with the officers. When the record is silent, the
inference is inescapable that he kept his mouth shut.

   If Lopez was not himself the gunman, it was probable that
he was in on the gunman’s scheme. The police knew that the
gunman was part of a drug conspiracy. Why else would the
gunman have tried to use a gun to stop a police narcotics
investigation? It was reasonable to think that a conspiracy of
this kind, leading to an act of violence against law enforce-
ment, must have more than two members. The chances were
fair that the gunman would not himself return to the car but
use another member of the gang to get it. Arriving, after dark,
in a car whose windows were tinted so darkly that they vio-
lated state law, Lopez drove directly to the car that had been
used in the attempted shooting earlier in the day, dropped off
a driver with keys fitting that car, and then, after the kind of
evasive maneuvers designed to thwart surveillance, had fol-
lowed the Focus. There was a fair probability that Lopez’s
actions were those of, if not the gunman himself, then a fel-
low conspirator.

   As long as Lopez did not offer an explanation of his role
— and the record shows no evidence that he did at the police
station — a police officer could reasonably believe that they
had in custody either the gunman himself or another partici-
pant in the drug conspiracy the gunman was trying to defend
by his desperate assault on the police. Either way, probable
cause was present and undiminished at the time that Lopez
consented to the search of his car.
