Sack, Circuit Judge

Robert W. Allen (Anna M. Skotko, on the brief), Assistant United States Attorney, for Joon H. Kim, Acting United States Attorney for the Southern District of New York, for Appellee.

Daniel Habib , Federal Defenders of New York, Inc., Appeals Bureau, New York, NY, for Defendant–Appellant.

Jordan Wells, Alexis Karteron, (on the brief), for Amicus Curiae New York Civil Liberties Union Foundation.

Before: Walker, Sack, and Chin, Circuit Judges.

Sack, Circuit Judge:

During a routine patrol of a Bronx apartment building, New York City Police Department ("NYPD") Officer Chris Aybar observed defendant Jose Diaz sitting in a stairwell while holding a plastic cup that seemed to Aybar to smell of alcohol. Officer Aybar initially intended only to issue Diaz a summons—not to make an arrest—for violating New York's open-container law. She ordered him to stand against the wall and produce identification. Diaz stood and then, as if to retrieve something, fumbled with his hands in his jacket pockets and rearranged his waistband. Officer Aybar frisked Diaz and felt a bulge on the side of his jacket; she opened his jacket pocket and discovered a loaded handgun. She then arrested Diaz, who was later found guilty, by the presiding district judge (Jesse M. Furman, Judge ) acting as trier of fact, of being a previously convicted felon in possession of a firearm in violation of 18 U.S.C. § 922(g). He received a sentence of thirty-three months' imprisonment.

Before the trial, Diaz filed a motion to suppress evidence about the presence of the gun on Fourth Amendment grounds. The district court denied the motion, concluding that the search was a lawful search incident to an arrest supported by probable cause. Having thereafter been convicted, Diaz now appeals that denial, arguing that (1) Officer Aybar lacked probable cause to arrest and search Diaz for violating New York City's open-container law, N.Y.C. Admin. Code § 10–125(b), because an apartment-building stairwell is not a "public place" within the meaning of that law, and (2) in any event, the warrantless search was not a lawful search incident to an arrest because Officer Aybar did not intend to arrest Diaz when she began the search.

We disagree. We conclude that Officer Aybar had probable cause to arrest Diaz inasmuch as she had a reasonable belief that an apartment-building stairwell is a public place for purposes of the open-container law and that Diaz was violating that law. And because she had probable cause to arrest Diaz—and ultimately did arrest him—the warrantless search was a lawful search incident to an arrest, even though Officer Aybar testified that before finding the gun she intended only to issue a summons, not to make an arrest.

BACKGROUND

On the night of March 21, 2015, NYPD Officers Chris Aybar and Jose Espinal entered a four-story, twelve-unit private apartment building located at 584 East 167th Street in New York City's Borough of the Bronx, to conduct a floor-by-floor patrol as part of the NYPD's "Clean Halls" program, pursuant to which officers enter common spaces in residential buildings with the building owner's consent in an effort to deter crime, principally drug dealing and trespassing. Upon entering the apartment building through the front door, which was propped open with a newspaper, the officers immediately smelled marijuana.

They proceeded to climb the stairs to the third-floor landing, where they saw three men: defendant Jose Diaz, Collin Maloney, and Joshua Knox. Diaz was sitting next to a bottle of vodka and holding a red plastic cup. As Officer Aybar approached Diaz, she saw clear liquid in the cup and smelled what seemed to be alcohol. Maloney was also holding a red plastic cup, and Knox was holding a lit "blunt" (marijuana cigarette) in one hand and a box of "roaches" (butts of smoked marijuana cigarettes) in the other.

Officer Aybar testified that she did not initially intend to arrest Diaz, only to issue him a summons for violating New York's open-container law, which provides that "[n]o person shall drink or consume an alcoholic beverage, or possess, with intent to drink or consume, an open container containing an alcoholic beverage in any public place...." N.Y.C. Admin. Code § 10–125(b). Officer Aybar had previously received training on the open-container law and had issued approximately fifty summonses for open-container violations, often in apartment buildings.

Because Officer Aybar did not feel safe confronting Diaz while he was seated, she ordered him to stand against the wall and produce his identification. Diaz stood, and then, as if to retrieve something, fumbled with his hands in his jacket pockets and rearranged his waistband. Fearing, because of his movements, that her safety was threatened, Officer Aybar frisked Diaz and felt a bulge on his jacket. She opened his jacket pocket and discovered a loaded .380 caliber Taurus firearm. She then handcuffed Diaz and transported him to the police station, where she issued him a summons for the open-container violation.

On May 5, 2015, a grand jury returned a single-count indictment charging Diaz with possessing a firearm as a previously convicted felon in violation of 18 U.S.C. § 922(g). Diaz filed a motion to suppress evidence concerning the firearm on Fourth Amendment grounds. On July 24, 2015, during an evidentiary hearing on that motion, Diaz testified that (1) he was not drinking alcohol in the apartment-building stairwell; (2) he produced his identification when Officer Aybar asked for it; and (3) Officer Aybar took the jacket (which he was not wearing) from him and searched it rather than frisking him.

Following the hearing, the district court denied the suppression motion by opinion and order dated August 14, 2015. See United States v. Diaz , 122 F.Supp.3d 165, 181 (S.D.N.Y. 2015). Crediting the officers' testimony over that of Diaz, id . at 168, the district court found that "Officer Aybar indisputably had probable cause to believe that Diaz was drinking alcohol or possessing alcohol with intent to drink it," based on Officer Aybar's testimony that "she smelled alcohol" and "observed Diaz holding a red [plastic] cup containing a clear liquid while sitting in close proximity to an open bottle of vodka," id . at 173.

The district court rejected Diaz's argument that Officer Aybar lacked probable cause to arrest him on the ground that an apartment-building stairwell is not a "public place" within the meaning of the open-container law. See id . at 173–76. It noted that "a compelling argument [could] certainly be made that the common areas of residential buildings do not qualify as public places for purposes of the [ ] law," but ultimately concluded that it "need not resolve that unsettled question of state law because, even if Officer Aybar was mistaken in her belief that the stairwell qualified as a ‘public place’ for purposes of the open-container law, her mistake was an objectively reasonable one" that did not violate the Fourth Amendment. Id . at 174.

The district court also rejected Diaz's argument that the search could not be justified as a search incident to an arrest because Officer Aybar did not intend to arrest Diaz until after she found the gun. See id . at 176–81. In reaching this conclusion, it relied on United States v. Ricard , 563 F.2d 45 (2d Cir. 1977), where we held that a search conducted in similar circumstances was a constitutional search incident to an arrest, id . at 49. The district court noted, however, a tension between Ricard and the Supreme Court's subsequent decision in Knowles v. Iowa , 525 U.S. 113, 119 S.Ct. 484, 142 L.Ed.2d 492 (1998), in which it held unlawful a search conducted after an officer had already issued a citation for a traffic infraction. See Diaz , 122 F.Supp.3d at 178–80 (citing Knowles , 525 U.S. at 117–19, 119 S.Ct. 484 ).

After the district court denied Diaz's motion to suppress, the case proceeded to a bench trial on stipulated facts. On September 11, 2015, Diaz was found guilty of possessing a firearm as a previously convicted felon in violation of 18 U.S.C. § 922(g). He received a sentence of thirty-three months' imprisonment. This appeal followed.

DISCUSSION

Diaz appeals from the denial of his motion to suppress evidence concerning the gun found in his jacket on the grounds that (1) Officer Aybar lacked probable cause to conduct the search, and (2) in any event, the warrantless search was not justified as a search incident to an arrest because Officer Aybar did not intend to arrest him when she began the search. We disagree in both respects.

I. Standard of Review

"On appeal from a district court's ruling on a motion to suppress evidence, we review legal conclusions de novo and findings of fact for clear error." United States v. Ganias , 824 F.3d 199, 208 (2d Cir. 2016) (en banc ) (internal quotation marks omitted). "We also review de novo mixed questions of law and fact," and "pay special deference to the district court's factual determinations going to witness credibility." United States v. Bershchansky , 788 F.3d 102, 108 (2d Cir. 2015) (emphasis and internal quotation marks omitted).

II. Probable Cause

Diaz's first argument fails because at the time of the search, Officer Aybar had probable cause to arrest Diaz for a violation of New York's open-container law based on a reasonable belief that an apartment-building stairwell is a public place for purposes of that law.

A police officer ordinarily has probable cause to arrest when he or she "ha[s] knowledge of, or reasonably trustworthy information as to, facts and circumstances that are sufficient to warrant a person of reasonable caution in the belief that an offense has been or is being committed by the person to be arrested." Manganiello v. City of New York , 612 F.3d 149, 161 (2d Cir. 2010) (internal quotation marks omitted). An officer's assessment in this regard need not "be perfect" because "the Fourth Amendment allows for some mistakes on the part of government officials," including "reasonable ... mistakes of law." Heien v. North Carolina , ––– U.S. ––––, 135 S.Ct. 530, 536, 190 L.Ed.2d 475 (2014) ; see also Herring v. United States , 555 U.S. 135, 139, 129 S.Ct. 695, 172 L.Ed.2d 496 (2009) ("When a probable-cause determination was based on reasonable but mistaken assumptions, the person subjected to search or seizure has not necessarily been the victim of a constitutional violation.").

Officer Aybar's probable-cause determination was predicated on the New York open-container law, which provides that "[n]o person shall drink or consume an alcoholic beverage, or possess, with intent to drink or consume, an open container containing an alcoholic beverage in any public place," N.Y.C. Admin. Code § 10–125(b), where "public place" is defined, in pertinent part, as "[a] place to which the public or a substantial group of persons has access, including, but not limited to, any highway, street, road, sidewalk, parking area, shopping area, place of amusement, playground, park or beach located within the city," id . § 10–125(a)(2). Diaz argues that the apartment-building stairwell where he was found with an open container of alcohol is not a "public place" because, although it is a common area, it is located within a locked residential building. In his view, canons of construction such as ejusdem generis and noscitur a sociis support his construction of the open-container law. But as the district court correctly acknowledged, Diaz , 122 F.Supp.3d at 174–75, the question presented here is not whether a common area of an apartment such as a stairwell constitutes a public place within the meaning of the open-container law, but only whether Officer Aybar had an objectively reasonable belief that it so qualified.

The Supreme Court's decision in Heien provides clear guidance in this regard. There, two North Carolina police officers found cocaine in a vehicle they had stopped because one of its two tail lights was inoperative, which the officers believed to be a violation of state law. Heien , 135 S.Ct. at 534, 540. This belief turned out to be mistaken; on appeal, a state appellate court determined that the applicable state law required only one working tail light. Id . at 535, 540. The Supreme Court held that the stop (and subsequent search), although premised on an erroneous understanding of the traffic law, was nonetheless constitutional because "reasonable suspicion can rest on a mistaken understanding of the scope of a legal prohibition," id . at 536, so long as that mistaken understanding was "objectively reasonable," id . at 539 (emphasis omitted). That was so in Heien because, at the time of the stop, the North Carolina tail-light law was ambiguous, and the state's appellate courts had not previously resolved the ambiguity. See id . at 540.

The test for whether an officer's mistake of law was objectively reasonable "is not as forgiving as the one employed in the distinct context of deciding whether an officer is entitled to qualified immunity," id . at 539, often where a party brings a claim under Bivens or 42 U.S.C. § 1983 for a violation of their constitutional rights. Cf. Heien , 135 S.Ct. at 539–40 ("[A]n officer can gain no Fourth Amendment advantage through a sloppy study of the laws he is duty-bound to enforce."). Indeed, as Justice Kagan explained in her concurring opinion in Heien , "the test is satisfied [only] when the law at issue is so doubtful in construction that a reasonable judge could agree with the officer's view." Id . at 541 (Kagan, J., concurring) (internal quotation marks omitted); see also United States v. Stanbridge , 813 F.3d 1032, 1037 (7th Cir. 2016) (concluding that statutory ambiguity is a prerequisite to a determination that an officer's mistake of law was objectively reasonable); United States v. Alvarado–Zarza , 782 F.3d 246, 250 (5th Cir. 2015) (same).

We think that Officer Aybar's belief that the apartment-building stairwell qualified as a "public place" within the meaning of the open-container law was an objectively reasonable prediction of the scope of the law when it was made. As in Heien , her assessment was premised on a reasonable interpretation of an ambiguous state law, the scope of which had not yet been clarified. Even now, the New York Court of Appeals has not addressed whether a common area inside an apartment building is a "public place" within the meaning of the open-container law, and the other New York courts that have done so have reached conflicting conclusions. Compare People v. Medina , 16 Misc.3d 382, 389, 842 N.Y.S.2d 227, 232, (Sup. Ct. Bronx Cty. 2007) (concluding that an apartment-building lobby is a "public place" for purposes of the open-container law), with People v. Chavez , 41 Misc.3d 526, 533–34, 972 N.Y.S.2d 858, 862–63, (Crim. Ct. Bronx Cty. 2013) (concluding that an apartment-building elevator is not a "public place" within the meaning of the open-container law); see also United States v. Brown , No. 07-CV-232 (JBW), 2007 WL 2121883, at *2–4, 2007 U.S. Dist. LEXIS 54057, at *6-8 (E.D.N.Y. July 25, 2007) (relying on Medina to conclude that a bodega is a "public place" within the meaning of the open-container law). In light of these conflicting precedents, Officer Aybar's belief that an apartment-building stairwell is a public place within the meaning of the open-container law was a reasonable, even if mistaken, assessment of the scope of that law at the time it was made. Thus, contrary to Diaz's contention, Officer Aybar had probable cause to believe that Diaz had violated the open-container law.

III. Search Incident to an Arrest

Diaz next contends that the search was not a lawful search incident to an arrest because, at the time of the search, Officer Aybar did not intend to arrest Diaz and would not have ultimately done so had she not discovered the gun as a fruit of the search. We are not persuaded.

The search-incident-to-arrest doctrine is an exception to the general requirement that an officer must obtain a judicial warrant supported by probable cause before conducting a search. See Riley v. California , –––U.S. ––––, 134 S.Ct. 2473, 2482, 189 L.Ed.2d 430 (2014) (recognizing a search incident to an arrest as a "specific exception" to the Fourth Amendment's warrant requirement). It serves two interests: "protecting arresting officers and safeguarding any evidence of the offense of arrest that an arrestee might conceal or destroy." Arizona v. Gant , 556 U.S. 332, 339, 129 S.Ct. 1710, 173 L.Ed.2d 485 (2009). These interests are not evaluated on a case-by-case basis, but are assumed to be present whenever an officer is justified in making an arrest. Riley , 134 S.Ct. at 2483. It makes no difference whether the search occurs before or after the arrest, see Rawlings v. Kentucky , 448 U.S. 98, 111, 100 S.Ct. 2556, 65 L.Ed.2d 633 (1980), so long as it is "substantially contemporaneous with the arrest and is confined to the immediate vicinity of the arrest," Shipley v. California , 395 U.S. 818, 819, 89 S.Ct. 2053, 23 L.Ed.2d 732 (1969) (internal quotation marks omitted).

In United States v. Ricard , 563 F.2d 45 (2d Cir. 1977), we squarely addressed whether a search incident to an arrest can be justified where an officer did not intend to make an arrest prior to conducting the search, see id . at 48. The officer there did not initially intend to arrest a driver stopped for speeding, but after a search of a small tinfoil packet revealed cocaine, the officer made an arrest. Id . at 48–49. We held that the search was lawful because the officer had probable cause to arrest the defendant for speeding, regardless of whether or not the officer intended to arrest the defendant before discovering the cocaine. Id . at 49 (explaining that, although "the contested search was actually the cause of [the defendant's] arrest[,] ... the fact that [the officer] had cause to arrest [the defendant] for speeding, even if he initially determined not to do so, was a sufficient predicate for a full search [incident to an arrest]").

Diaz has conceded that Ricard controls if it continues to be precedential and therefore binding on us, but contends that it does not remain binding precedent in light of the Supreme Court's decision in Knowles v. Iowa , 525 U.S. 113, 119 S.Ct. 484, 142 L.Ed.2d 492 (1998). There, a police officer, who had probable cause to arrest a defendant stopped for speeding, issued a citation for the speeding violation before conducting a full search of the car that revealed marijuana, prompting an arrest. Id . at 114, 119 S.Ct. 484. The Supreme Court held that the arrest could not be justified as a search incident to an arrest. Id . at 117–19, 119 S.Ct. 484. Although it acknowledged "that the authority to conduct a full field search as incident to arrest [is] a bright-line rule" that is "based on the concern for officer safety and destruction or loss of evidence, but which d[oes] not depend in every case upon the existence of either concern," id . at 118, 119 S.Ct. 484 (internal quotation marks), the Court "decline[d]" to "extend that ‘bright-line rule’ to a situation where the concern for officer safety is not present to the same extent and the concern for destruction or loss of evidence is not present at all," namely where a citation for speeding had already been issued during a routine traffic stop, id . at 118–19, 119 S.Ct. 484 ; see also id . at 117–18, 119 S.Ct. 484 (explaining that "[t]he threat to officer safety from issuing a traffic citation ... [was] a good deal less than in the case of a custodial arrest," and that the need-to-preserve-evidence rationale was not implicated because "[o]nce [the defendant] was stopped for speeding and issued a citation, all the evidence necessary to prosecute that offense had been obtained").

Knowles can in some respects be likened to Ricard . The officers in both cases had probable cause to arrest the defendants for speeding but initially elected not to do so, and then proceeded to conduct searches that revealed evidence of crimes for which the defendants were ultimately arrested. But critically, the search in Knowles occurred after the officer had completed the traffic stop by issuing a citation, whereas the search in Ricard (and the case at bar) occurred before any such event took place. It thus remained uncertain in Ricard (and here) whether the encounter would lead to an arrest; the dangers to the officer that accompany the prospect of arrest therefore remained present. See Knowles , 525 U.S. at 117, 119 S.Ct. 484 (explaining that "[t]he danger to the police officer flows from the fact of arrest, and its attendant proximity, stress, and uncertainty" (internal quotation marks omitted)). In Knowles , by contrast, those dangers had virtually vanished by the time the officer issued the citation, which extinguished the prospect of an arrest. We therefore do not understand Knowles to foreclose a search incident to an arrest in circumstances where, as in Ricard and the case before us, an officer has not yet issued a citation and ultimately makes a lawful arrest after conducting a search, regardless of whether or not the officer intended to do so prior to the search. Where there is a basis for an arrest, an officer has reason to be concerned for her safety until she issues a citation and the stop ends. Cf. Rodriguez v. United States , ––– U.S. ––––, 135 S.Ct. 1609, 1612, 191 L.Ed.2d 492 (2015) ("A seizure justified only by a police-observed traffic violation ... becomes unlawful if it is prolonged beyond the time reasonably required to complete the mission of issuing a ticket for the violation." (internal quotation marks and brackets omitted)).

Our conclusion comports with those of other circuits addressing the scope of Knowles . See, e.g. , United States v. Chauncey , 420 F.3d 864, 872 (8th Cir. 2005) (rejecting the defendant's "attempt[ ] to liken his case to Knowles " because "[w]hatever the officer's subjective intention, [ ] the record does not show that the officer had completed the traffic stop by the time he made a formal arrest"); United States v. Bookhardt , 277 F.3d 558, 566 (D.C. Cir. 2002) (limiting Knowles to circumstances where "[an] officer [with] probable cause to make an arrest ... issues a citation instead of arresting the defendant"); see also United States v. Williams , 170 Fed.Appx. 399, 405 (6th Cir. 2006) (unpublished opinion) (concluding that there is a "significant difference between Knowles and the present case" because "[i]n Knowles , the officers issued the defendant a citation before they searched the vehicle" (emphasis in original)).

Arguing otherwise, Diaz asserts that Knowles stands for a broader proposition that overrules Ricard : An officer may conduct a search incident to an arrest only if she has already made an arrest or an arrest is impending. In support of this interpretation, he points to a recent New York Court of Appeals decision addressing the scope of Knowles . See People v. Reid , 24 N.Y.3d 615, 26 N.E.3d 237, 2 N.Y.S.3d 409 (2014). There, an officer who had probable cause to arrest a driver for driving while intoxicated ordered the driver out of the car, patted him down, discovered a switchblade knife, and arrested him for criminal possession of a weapon. Id . at 618, 26 N.E.3d at 238, 2 N.Y.S.3d at 410. The officer testified that he did not initially intend to arrest the driver, but decided to do so only after he found knife. Id . Relying on Knowles , the court held that the search was unconstitutional on the ground that "to say that the search was incident to arrest does not make sense" where "but for the search there would have been no arrest at all." Id . at 619, 26 N.E.3d at 239, 2 N.Y.S.3d at 411.

We think his rationale is mistaken for two reasons. First, it ignores that an officer who stops a person to issue a citation faces an evolving situation. As events develop and new information becomes available—the presence of a gun, for example—a police officer is entitled to change her course of action. Cf. Graham v. Connor , 490 U.S. 386, 396–97, 109 S.Ct. 1865, 104 L.Ed.2d 443 (1989) ("The calculus of reasonableness must embody allowance for the fact that police officers are often forced to make split-second judgments[ ]in circumstances that are tense, uncertain, and rapidly evolving...."). Second, it appears to require a court to consider the officer's intent at the time of arrest, an inquiry at odds with the Supreme Court's "repeated[ ] reject[ion of] a subjective approach" in the Fourth Amendment context. Fernandez v. California , ––– U.S. ––––, 134 S.Ct. 1126, 1134, 188 L.Ed.2d 25 (2014) (internal quotation marks omitted); see also Kentucky v. King , 563 U.S. 452, 464, 131 S.Ct. 1849, 179 L.Ed.2d 865 (2011) ("[W]e have never held, outside limited contexts such as an inventory search or administrative inspection ..., that an officer's motive invalidates objectively justifiable behavior under the Fourth Amendment." (ellipsis in original) (internal quotation marks omitted)).

Diaz insists that no subjective inquiry is necessary to determine whether an arrest was occurring or about to occur at the time of the search. That question, in his view, can be answered on a case-by-case basis by looking only to objective evidence such as, inter alia , an officer's contemporaneous statements, the length of any pre-search detention, the issuance of a citation, calls for backup, the presence or absence of handcuffs, and the treatment of similarly situated suspects at the scene.

But even if limited to objective evidence, the case-by-case approach runs counter to the principle "that the authority to conduct a full field search as incident to arrest [is] a bright-line rule." Knowles , 525 U.S. at 118, 119 S.Ct. 484 (internal quotation marks omitted). The Supreme Court has long recognized that in the Fourth Amendment context, there is "[a] need for [ ] bright-line constitutional standard[s]," Virginia v. Moore , 553 U.S. 164, 175, 128 S.Ct. 1598, 170 L.Ed.2d 559 (2008), which advance the "essential interest in readily administrable rules," Atwater v. City of Lago Vista , 532 U.S. 318, 347, 121 S.Ct. 1536, 149 L.Ed.2d 549 (2001). This interest undergirds the well-settled principle that searches incident to arrest are categorically justified and do not require "case-by-case adjudication" of their safety and evidentiary bases. United States v. Robinson , 414 U.S. 218, 235, 94 S.Ct. 467, 38 L.Ed.2d 427 (1973).

Thus, we conclude that, contrary to the Reid court's interpretation, Knowles does not require case-by-case determinations as to whether or not an arrest was impending at the time of the search; it instead stands for the proposition that the bright-line search-incident-to-arrest doctrine does not apply where an officer has completed the encounter by issuing a citation instead of making an arrest. That proposition of law has no bearing on Ricard , which therefore remains binding precedent that controls our analysis of this appeal. Accordingly, Officer Aybar's search of Diaz was a valid search incident to an arrest, despite the fact that she did not intend to arrest him when she began the search. See Ricard , 563 F.2d at 48–49.

* * *

In sum, we conclude that in the context of the facts of the case at bar, an officer like Officer Aybar, who has probable cause to believe that a person has committed a crime premised on an objectively reasonable mistake of law, may lawfully search that person pursuant to the search-incident-to-arrest doctrine, provided that a "formal arrest follow[s] quickly on the heels of" the frisk. Rawlings , 448 U.S. at 111, 100 S.Ct. 2556. It was irrelevant whether, at the time of the search, Officer Aybar intended to arrest Diaz or merely to issue him a citation.

CONCLUSION

For the foregoing reasons, we AFFIRM the judgment of the district court.