Callahan v. Wilson, 863 F.3d 144

Background

On Sept. 20, 2011, Suffolk County Officer Thomas Wilson entered Kevin Callahan’s home after a radio report that Callahan said another person there had a gun; officers announced themselves and searched the house.
Wilson encountered Callahan behind a partially open bedroom door, claimed the door pinned him and that he saw a shadow/hand with an unknown object; Wilson fired four shots, three struck Callahan, who died; no weapon was found in the bedroom.
Plaintiffs (Callahan’s mother and brother/estate) sued under 42 U.S.C. § 1983 alleging excessive (deadly) force in violation of the Fourth Amendment; the case was tried and the jury returned a verdict for Officer Wilson.
Plaintiffs preserved an objection to the district court’s jury instruction on deadly force, arguing the charge failed to track this Circuit’s Rasanen formulation that deadly force is unreasonable unless the officer had probable cause to believe the suspect posed a significant threat of death or serious physical injury.
The district court instructed generally on objective reasonableness and used permissive language—"a police officer may use deadly force if [he] has probable cause…"—rather than the restrictive "only/unless" language that Rasanen requires.
The Second Circuit held the instruction was inconsistent with Rasanen, concluded the error was not harmless, vacated the judgment, and remanded for a new trial; it also affirmed the exclusion of certain expert testimony and prior-acts evidence as within the district court’s discretion.

Issues

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the jury charge on deadly force misstated Circuit law	The court failed to instruct that deadly force is unreasonable unless the officer had probable cause to believe the suspect posed a significant threat of death or serious injury (Rasanen).	The court’s instruction ("may use deadly force if [probable cause]") was sufficient; Plumhoff and Mendez do not undermine the instruction; jury was focused on probable cause.	The charge was erroneous under Rasanen because permissive "may/if" language does not convey exclusivity; reversal and new trial ordered.
Whether the instructional error was harmless	The error could have allowed the jury to rely on a general reasonableness standard rather than the Rasanen probable-cause rule; thus it likely affected verdict.	The parties’ summations focused exclusively on probable cause, so any error was harmless.	Error was not harmless; court could not conclude the jury relied on the required probable-cause standard.
Admissibility of expert testimony on police protocol (Zogbi)	Testimony was relevant to whether officers used proper room-clearing techniques and thus to excessiveness of force.	Expert’s opinions about training and proper tactics were not probative of the dispositive question—probable cause—and would usurp the jury’s role.	Exclusion was within district court’s discretion (no abuse): testimony was not sufficiently relevant and risked usurping the jury.
Admissibility of Officer Wilson’s prior discharges at dogs	Prior incidents show state of mind and propensity to use deadly force; admissible under Rule 404(b) for intent/credibility.	Prior incidents were prejudicial and of limited probative value; district court properly excluded them.	Exclusion was within district court’s discretion: prejudicial effect outweighed probative value.

Key Cases Cited

Rasanen v. Doe, 723 F.3d 325 (2d Cir. 2013) (required jury instruction: deadly force is unreasonable unless officer had probable cause to believe suspect posed significant threat of death or serious physical injury)
Plumhoff v. Rickard, 134 S. Ct. 2012 (U.S. 2014) (application of objective-reasonableness analysis to police use of deadly force in high-speed chase context)
County of Los Angeles v. Mendez, 137 S. Ct. 1539 (U.S. 2017) (reaffirming reasonableness as the operative framework in excessive-force cases and rejecting a Ninth Circuit provocation rule)
Scott v. Harris, 550 U.S. 372 (U.S. 2007) (reasonableness governs Fourth Amendment use-of-force claims; Garner is an application, not a separate on/off rule)
Tennessee v. Garner, 471 U.S. 1 (U.S. 1985) (police may use deadly force when officer has probable cause to believe suspect poses significant threat of serious physical harm)
Uzoukwu v. City of New York, 806 F.3d 409 (2d Cir. 2015) (harmless-error standard for erroneous jury instructions)
O’Bert v. Vargo, 331 F.3d 29 (2d Cir. 2003) (discussing application of Garner principles in qualified-immunity/summary-judgment context)