United States Court of Appeals
                       For the First Circuit


No. 17-1180

                      EDUARDO SOTO-CINTRÓN,
    on his own behalf and on behalf of his minor son A.S.M.;
                          A.S.M., Minor,

                       Plaintiffs, Appellants,

                         WINDY MARRERO-COLÓN,
              solely on behalf of her minor son A.S.M.,

                             Plaintiff,

                                 v.

                           UNITED STATES,

                        Defendant, Appellee.


          APPEAL FROM THE UNITED STATES DISTRICT COURT
                 FOR THE DISTRICT OF PUERTO RICO

        [Hon. Salvador E. Casellas, U.S. District Judge]


                               Before

                         Howard, Chief Judge,
                 Lipez and Thompson, Circuit Judges.


     Jorge Martínez-Luciano, with whom Emil Rodríguez-Escudero was
on brief, for appellants.
     Mainon A. Schwartz, Assistant United States Attorney, with
whom Rosa Emilia Rodríguez-Vélez, United States Attorney, and
Thomas F. Klumper, Assistant United States Attorney, Acting Chief,
Appellate Division, were on brief, for appellee.
August 20, 2018
           LIPEZ, Circuit Judge.          Plaintiff Eduardo Soto-Cintrón

and his 17-year-old son went to a post office in Coto Laurel,

Puerto Rico to pick up some mail.           While Soto-Cintrón waited in

his red Ford F-150 truck, his son retrieved some envelopes from

the post office and returned to his father's vehicle.         As the two

pulled out of the parking lot, they were stopped by a number of

federal law enforcement agents with guns drawn.         Soto-Cintrón was

removed from his vehicle and handcuffed, and he and his son were

detained for up to twenty minutes.

           The agents from the Bureau of Alcohol, Tobacco, Firearms

and Explosives ("ATF") had stopped the wrong people.           Once they

realized their mistake, the agents arrested the person who had

received the illegal shipment of firearms, and released Soto-

Cintrón and his son.     Soto-Cintrón later filed a claim against the

United States under the Federal Tort Claims Act ("FTCA") for false

imprisonment.   The district court granted summary judgment to the

government, and Soto-Cintrón appealed.           Though our analysis of

Soto-Cintrón's FTCA claim differs from the district court's, we

ultimately reach the same conclusion, and affirm.

                                     I.

           In May 2013, the United States Postal Inspection Service

("USPIS") intercepted a package sent from Orlando, Florida to

Puerto Rico.    Suspecting that the package contained six illegal

Glock   semi-automatic    pistols,    USPIS    personnel   requested   the


                                 - 3 -
assistance of the ATF to set up a controlled delivery.                        The

agencies devised a plan to leave a notice at the addressee's

residence informing him that he could claim the package at the

U.S. Post Office in Coto Laurel.                Pursuant to the plan, USPIS

personnel would assume the primary surveillance positions inside

the post office and in the parking lot, while ATF agents would be

posted around the perimeter of the parking lot.               Whoever showed up

to collect the package would be arrested, as would anyone else

linked to the receipt of the package.

             During   the     operation,    a   USPIS     inspector   used   radio

communication to announce the separate arrival of two vehicles to

the post office parking lot.             First, the inspector identified a

red   Ford   F-150    which    turned    out    to   be   Soto-Cintrón's.      The

inspector stated that the occupants of the vehicle remained seated

for some amount of time before the younger occupant went into the

post office.     Second, the inspector announced the arrival of a

white Ford F-150 which, as it turned out, was driven by the

suspect.

             While both vehicles were still in the parking lot, the

USPIS inspector broadcasted that the package had been delivered to

the suspect.     Then, without identifying which vehicle the suspect

placed the package in, the radio operator stated that the red Ford

F-150 -- belonging to Soto-Cintrón -- was leaving the parking lot.




                                        - 4 -
            One of the ATF agents on the receiving end of these radio

communications    was   Special   Agent   Vladimir    González.   He   was

stationed on an access road at the perimeter of the parking lot in

a vehicle driven by ATF Task Force Officer Jose Fajardo, and also

occupied by Special Agent Raul Peña-López.            When Special Agent

González heard the radio transmissions he could not discern which

truck contained the suspicious package.              After unsuccessfully

attempting to obtain clarification from a USPIS inspector, he made

the decision to stop the red truck driven by Soto-Cintrón before

it could leave the parking lot.      Special Agent González instructed

Officer Fajardo to block the parking lot exit with his vehicle,

and the three agents approached Soto-Cintrón's truck with guns

drawn, identifying themselves as police and ordering Soto-Cintrón

and his son to put their hands up.

            Soto-Cintrón and his son had the windows rolled up and

the air conditioning and radio turned on, so they could not hear

the agents' commands.     One of the officers pulled Soto-Cintrón out

of his vehicle, handcuffed him, and placed him face down on the

pavement.    His son was also handcuffed and placed next to him, but

was soon uncuffed and allowed to sit on the ground away from the

vehicle.    The agents questioned Soto-Cintrón about the package and

performed a visual inspection of his truck.              Soto-Cintrón, of

course, denied any knowledge of the illegal firearms, and the

agents' visual inspection did not reveal the suspicious package.


                                  - 5 -
          At   some   point   during   Soto-Cintrón's   detention,   the

agents learned that the actual suspect -- the person in the white

truck -- had been apprehended, and that Soto-Cintrón and his son

were not involved in the illegal firearms delivery.         The agents

accordingly released Soto-Cintrón and his son.          Their detention

lasted approximately fifteen to twenty minutes.

          Based on this incident, Soto-Cintrón sued the United

States in February 2015.1       The complaint alleges that the ATF

agents committed false imprisonment under Puerto Rico law and that

the United States is liable for the tort under the FTCA.         See 28

U.S.C. §§ 2674, 2680(h).2     Following a period of discovery in which

Soto-Cintrón chose not to conduct any depositions, the government

moved for summary judgment, arguing primarily that Soto-Cintrón's

detention constituted a Terry stop based on the ATF agents'

reasonable suspicion of criminal activity.      See Terry v. Ohio, 392

U.S. 1 (1968). The district court granted the government's motion,

explaining that Puerto Rico would not impose tort liability for



     1 More specifically, Soto-Cintrón sued on his own behalf and
on behalf of his minor son, and the minor's mother, Windy Marrero-
Colón, also sued on her son's behalf. We refer to Soto-Cintrón as
the sole plaintiff for simplicity.
     2 The complaint also asserts a claim for assault under Puerto
Rico law, but that claim is dependent on the success of Soto-
Cintrón's false imprisonment claim. Because we affirm the district
court's grant of summary judgment to the government on the false
imprisonment claim, we do not need to separately address the
assault claim. That claim necessarily fails as well.


                                  - 6 -
false imprisonment where an officer conducts a stop based on his

reasonable suspicion of criminal activity.            See id. at 30.

                 On appeal, Soto-Cintrón contends that the court erred by

importing Terry's reasonable suspicion standard into Puerto Rico

tort law.         He argues that Puerto Rico requires officers to meet a

more demanding "reasonable cause" standard, which both parties

treat       as    interchangeable   with    the   familiar    probable   cause

standard.        Abandoning its Terry argument,3 the government counters

that       the   ATF   agents   satisfied   Puerto   Rico's   reasonable   (or

probable) cause standard.           Alternatively, it argues that even if

the agents did not have probable cause to arrest, Puerto Rico would

not impose liability for false imprisonment because they would be

entitled to qualified immunity if plaintiffs had filed a Bivens

claim.       We agree with the government's alternative argument, and

affirm.




       3
       At oral argument, the government denied that it had
abandoned its Terry theory, asserting instead that it had merely
shifted focus to its other positions.      We find this argument
untenable. The government's response brief repeatedly refers to
the appropriate standard for false imprisonment under Puerto Rico
law as being "reasonable cause," and does not even cite to Terry.
It is axiomatic that arguments not developed on appeal are
abandoned. See United States v. Zannino, 895 F.2d 1, 17 (1st Cir.
1990).


                                      - 7 -
                                 II.

          A. The FTCA and Puerto Rico False Imprisonment Legal
          Standards

          The FTCA provides "a limited congressional waiver of the

sovereign immunity of the United States for tortious acts and

omissions committed by federal employees acting within the scope

of their employment."   Díaz-Nieves v. United States, 858 F.3d 678,

683 (1st Cir. 2017).      In an amendment to the FTCA, Congress

expressly waived sovereign immunity for false imprisonment when

the tort is committed by a "law enforcement officer[] of the United

States Government."     Pub. L. No. 93-253, 88 Stat. 50 (1974)

(codified at 28 U.S.C. § 2680(h)); see also Solis-Alarcón v. United

States, 662 F.3d 577, 583 (1st Cir. 2011).         The government's

liability under the FTCA is coextensive with that of "a private

individual under like circumstances."    28 U.S.C. § 2674.   We look

to local law to determine whether the government is liable for its

agents' allegedly tortious conduct.     See Díaz-Nieves, 858 F.3d at

683; 28 U.S.C. § 1346(b)(1).    "In this case, then, we must extract

the substantive rules of decision from Puerto Rico law." Calderón-

Ortega v. United States, 753 F.3d 250, 252 (1st Cir. 2014).

          Puerto Rico imposes liability for false imprisonment

when "[a] person, whether or not a law enforcement officer,"

tortiously or negligently "detain[s] or cause[s] the unlawful

detention of another person."    Ayala v. San Juan Racing Corp., 12



                                - 8 -
P.R. Offic. Trans. 1012, 1021 (P.R. 1982); see also P.R. Laws Ann.

tit. 31, § 5141 (imposing liability for fault or negligence that

causes injury).     To prevail on a false imprisonment claim, "it is

essential    that    the   individual        performing    the    arrest   lack

reasonable cause for believing that the arrestee committed a

felony."    Díaz-Nieves, 858 F.3d at 684.         This is so because Puerto

Rico    Criminal    Procedure   Rule    11    authorizes    law    enforcement

officers to make warrantless arrests where they have "reasonable

cause" to suspect that a person committed a felony.                  P.R. Laws

Ann. tit. 34a, Ap. II, § 11(c).

            "[A]side from the requirements of legality contained in

[Rule 11]," the Puerto Rico Supreme Court has explained that "we

should resort to the concept of the reasonable man" to assess

liability for false imprisonment.        Ayala, 12 P.R. Offic. Trans. at

1024.

            The reasonableness of the actions of a person
            sued in a civil action for damages for an
            alleged unlawful detention of the plaintiff,
            and his liability for them, should be weighed
            together with the following factors: the
            defendant's person, age, schooling, moral
            condition, and prior experience; the person,
            age, appearance and conduct of the detained
            person; knowledge that defendant had, on the
            day of the events, about the detained person
            and those people that had relations with him,
            suspicious conduct, including the seriousness
            of the crime it could imply, the place,
            occasion, and frequency of said conduct. This
            is in no way intended as an exhaustive list.
            Each case has its own characteristics, which



                                   - 9 -
           must be taken into account when determining
           whether or not there was a false arrest.

Id. at 1025.   Put another way, Puerto Rico imposes liability for

false imprisonment where, considering all the circumstances, an

arresting officer "not only makes a mistake" but also "incurs

negligence."   Valle v. Commonwealth of Puerto Rico, 157 D.P.R. 1,

24 (P.R. 2002) (emphases omitted)).

           We have interpreted this standard as being consistent

with federal qualified immunity principles -- a doctrine that

allows room for officers' "reasonable mistakes," Saucier v. Katz,

533 U.S. 194, 205 (2001), and protects from liability "all but the

plainly incompetent or those who knowingly violate the law,"

Malley v. Briggs, 475 U.S. 335, 341 (1986).        In Solis-Alarcón,

officers from the Drug Enforcement Agency ("DEA") had reason to

believe that a suspect in a major drug ring resided at the

plaintiffs' house.   662 F.3d at 579.     The DEA obtained an arrest

warrant for the suspect and, wielding guns, entered the house

without the plaintiffs' consent.    Id.   The officers then allegedly

detained the plaintiffs while they searched the house for 15-20

minutes.   Id. at 580.   They did not find the suspect at the house.

Id.

           Two years later, the plaintiffs brought a Bivens claim

against the DEA agents, alleging that the search violated the

Fourth Amendment, and a Puerto Rico false imprisonment FTCA claim



                                - 10 -
against the United States.           Id.; see also Bivens v. Six Unknown

Named Agents of Fed. Bureau of Narcotics, 403 U.S. 388, 389 (1971)

(recognizing a private right of action against federal agents for

violation of the Fourth Amendment).              The district court granted

summary    judgment    to   the    defendants     on    both   claims,    and    the

plaintiffs appealed.        Solis-Alarcón, 662 F.3d at 580.

            We first held that the DEA agents were entitled to

qualified immunity on the plaintiffs' Bivens claim.                      Under the

Fourth    Amendment,   officers      executing     an    arrest      warrant    at   a

residence must have a "reasonable belief that the target named in

the arrest warrant resides at the dwelling in question and will be

present at the time of the entry."               Id.    Given the information

available to the agents at the time, we concluded that even if

their "judgment" that the suspect resided at the plaintiffs' house

was "unreasonable, it was not 'manifestly unreasonable.'"                      Id. at

582 (quoting Ringuette v. City of Fall River, 146 F.3d 1, 5 (1st

Cir. 1998)).    Hence, "if there was error at all . . . it was not

so egregious as to defeat qualified immunity."                 Id.

            Having performed this qualified immunity analysis in the

Bivens context, we turned to the plaintiffs' false imprisonment

FTCA claim against the United States.             We reasoned that the scope

of liability under Puerto Rico's false imprisonment tort mirrored

the   federal   qualified         immunity     principles      that    applied       to

individual officers in a Bivens case.


                                      - 11 -
           Puerto Rico imposes liability for fault or
           negligence that causes injury, but protecting
           law enforcement agents for reasonable mistakes
           is common, and in at least two decisions, this
           court assumed that Puerto Rico tort law would
           not impose personal liability for mistaken
           arrests where the officers would be protected
           in Bivens claims by qualified immunity.

Id. at 583 (internal citations omitted) (referencing Abreu–Guzmán

v. Ford, 241 F.3d 69, 75-76 (1st Cir. 2001) and Rodriguez v. United

States, 54 F.3d 41, 45-47 (1st Cir. 1995)).    We further explained

that Puerto Rico recognizes the need to balance "the right to

compensation of a citizen who is injured by the wrongful or

negligent acts of a state officer," against "the duty of government

authorities to act vigorously in the investigation of criminal

causes."   Id. (quoting Valle, 157 D.P.R. at 25).      This was the

same "view that animates federal qualified immunity doctrine."

Id.

           Given   the   parallel   between   Puerto   Rico's   false

imprisonment tort and federal qualified immunity principles, we

held that the DEA agents who were entitled to qualified immunity

on the Bivens claim would not be subject to liability for false

imprisonment under Puerto Rico law.     And, because the agents did

not commit a tort, the United States was not liable for its agents'

actions under the FTCA.4


      4The Solis-Alarcón court also noted that if Puerto Rico's
false imprisonment jurisprudence had not mirrored qualified
immunity principles, "a significant question might arise whether


                               - 12 -
          B. Applying the Puerto Rico Law of False Imprisonment

          Viewing the facts in the light most favorable to Soto-

Cintrón, the ATF agents' actions reflect the type of reasonable

mistake for which Puerto Rico would not impose liability.            In

reaching this conclusion, we apply the reasonableness approach

detailed by the Ayala court, focusing on the "knowledge that

defendant had . . . about the detained person and those people

that had relations with him, suspicious conduct, including the

seriousness of the crime it could imply," as well as the other

factors identified there.    Ayala, 12 P.R. Offic. Trans. at 1025.

We also remain mindful of our precedent holding that the scope of

liability under Puerto Rico false imprisonment mirrors liability

under qualified immunity principles.       See Solis-Alarcón, 662 F.3d

at 583; Abreu–Guzmán, 241 F.3d at 75-76.

          Given   that   Special   Agent    González   initiated   Soto-

Cintrón's arrest, we focus our analysis on his knowledge at the


any local court could impose damage liability on federal officers
where they would be exempt in a federal lawsuit and whether
Congress under the FTCA would expect the federal government to
shoulder such liability." Id. at 583-84. Compare Norton v. United
States, 581 F.2d 390, 393 (4th Cir. 1978) (holding that the
government in an FTCA case is entitled to assert defenses available
to its agents individually), with Castro v. United States, 34 F.3d
106, 111 (2d Cir. 1994) (stating that "qualified immunity will not
immunize the United States from liability" in an FTCA case). The
Solis-Alarcón court did not need to answer this "significant
question," and neither do we. 662 F.3d at 583; cf. Guerra v.
Sutton, 783 F.2d 1371, 1375-76 (9th Cir. 1986) (declining to decide
whether qualified immunity "would . . . preclude recovery under
the [FTCA]").


                               - 13 -
time of that decision.          At that point, the radio operator had

announced that the suspect had left the post office with a package

containing six illegal firearms and then announced that the red

truck was leaving the parking lot. The temporal proximity of these

announcements led González to believe that the suspect -- who

González knew "matched the description of the driver of the white

Ford F-150" -- had placed the firearms in the red truck.              He could

"not think of any other reason why the USPIS inspector would have

announced the departure of the red Ford F-150," and, from his

experience, it was common for a person picking up an illegal

package to hand it off to someone else at the post office to

minimize the risk of being caught.             Still, he attempted to obtain

clarification from USPIS personnel about whether the firearms were

in   the   white   truck   or   the   red   truck,   but   his   efforts   were

unsuccessful.

            Despite this uncertainty, Special Agent González had to

make a decision.     On the one hand, if he let Soto-Cintrón's truck

leave the parking lot, he risked letting six illegal firearms make

their way into the community.           On the other, if he stopped the

truck, he risked detaining two innocent persons.                 Special Agent

González chose to stop the truck.           He directed Officer Fajardo to

block the parking lot exit with his vehicle, and González, Fajardo,

and Special Agent Peña-López initiated the arrest.               They released




                                      - 14 -
Soto-Cintrón and his son once it became clear that the two were

not involved in the firearms delivery.

           At worst, these facts show a team of agents making a

reasonable mistake -- in the heat of a dangerous moment -- about

the existence of the reasonable cause necessary to arrest Soto-

Cintrón and his son.   Indeed, "it is reasonable for police to move

quickly if delay 'would gravely endanger their lives or the lives

of others,'" even if when "judged with the benefit of hindsight,

the officers may have made 'some mistakes.'" City & Cnty. of S.F.,

Cal. v. Sheehan, 135 S. Ct. 1765, 1775 (2015) (applying qualified

immunity) (quoting Warden, Md. Penitentiary v. Hayden, 387 U.S.

294, 298-99 (1967) and Heien v. North Carolina, 135 S. Ct. 530,

536 (2014)).     As we have explained, Puerto Rico does not impose

tort liability for such mistakes.        See Solis-Alarcón, 662 F.3d at

583 (concluding that Puerto Rico's position is consistent with the

"common"   approach   of   "protecting    law   enforcement     agents   for

reasonable mistakes"); Abreu–Guzmán, 241 F.3d at 75-76 (holding

that   agents'   "objectively   reasonable      belief   that   there    was

probable cause . . . extinguishe[d] any basis for finding liability

for . . . false imprisonment" under Puerto Rico law).

           Soto-Cintrón's argument to the contrary is unavailing.

He contends that it could not have been reasonable for the ATF

agents to make the arrest because: (1) Special Agent González "had

eyes on" Soto-Cintrón and his son and thus knew that the son


                                - 15 -
returned from the post office with only a few envelopes in hand;

and (2) that it would be unreasonable to conclude that six Glock

pistols could fit in the envelopes.

            Even if we were to infer that Special Agent González

personally observed Soto-Cintrón's son, it would not undermine his

basis for stopping Soto-Cintrón's truck.          The radio operator told

González that "the package had been delivered to the suspect who

was then exiting the Post Office" and González knew that the

suspect "matched the description of the driver of the white Ford

F-150."    Thus, González's basis for stopping Soto-Cintrón's truck

was not that Soto-Cintrón's son had retrieved the package from the

post office and placed it in his father's truck. González believed

that the driver of the white truck was the one who received the

package.      His   suspicion   --   based   on    the   radio   operator's

communications regarding the red truck's exit from the parking lot

-- was that the driver of the white truck had placed the package

in Soto-Cintrón's truck.    González's supposed knowledge that Soto-

Cintrón's son returned from the post office carrying only envelopes

is irrelevant to the reasonableness of this suspicion.

            In sum, when the USPIS inspector's radio communications

caused confusion as to the whereabouts of the firearms,5 González



     5Soto-Cintrón does not allege that the USPIS radio operator's
actions created any tort liability for the United States under
Puerto Rico law.


                                 - 16 -
made the decision to prevent Soto-Cintrón and his son from leaving

the parking lot.    That reasonable decision would not expose the

arresting agents to liability for Puerto Rico false imprisonment,

and, given the vicarious liability premise of the FTCA, it does

not expose the United States to liability.

                               III.

          For the reasons discussed above, we affirm the district

court's judgment.

          So ordered.




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