FRAMINGHAM — A lawsuit filed by the family of a Framingham man who was accidentally shot and killed by police is now in the hands of a federal appeals court, which will determine whether the officer who pulled the trigger could face civil liability.

A three-judge panel of the U.S. Court of Appeals for the First Circuit heard oral arguments Dec. 10 from the legal team defending the town of Framingham and Officer Paul Duncan, who is named in a civil rights lawsuit brought by the family of Eurie Stamps Sr.

The court is weighing whether Duncan is immune from liability for the death because he was acting in his official capacity as a police officer when he fatally shot Stamps during a Jan. 5, 2011, police raid inside Stamps' apartment.

U.S. District Court Judge F. Dennis Saylor IV ruled last year that Duncan may have violated Stamps’ constitutional rights by disengaging the safety on his rifle and pointing the weapon at Stamps’ head as he lay on his stomach on the floor of his apartment.

Stamps was not a target of the raid and he had no history of violence, according to the judge’s ruling. SWAT team members were specifically informed that Stamps posed no known threat, and he did not struggle or resist police orders before he was killed, according to the ruling.

“Under the circumstances, a reasonable jury could find that Duncan’s actions leading up to the shooting were objectively unreasonable, and therefore that he employed excessive force in violation of the Fourth Amendment,” Saylor wrote in a December 2014 ruling.

Duncan and the town are challenging Saylor’s ruling, arguing Duncan's actions did not violate Stamps' rights under the Fourth Amendment, and that even if they did, Duncan is protected by the doctrine of qualified immunity because existing case law has not clearly established the circumstances under which injuries caused by an accidental discharge of a firearm by a police officer violates someone's constitutional rights.

Lawyer Leonard Kesten, who argued the case for the town, said federal courts have split on the matter, with some finding that a police shooting must be intentional in order to constitute a civil rights violation, and others determining an officer may be at fault — even if he or she didn't intend to shoot someone — if the officer's conduct leading up to the gunshot was "unreasonable."

Lawyer Anthony Tarricone, who is representing the Stamps family, countered during oral argument that federal courts have yet to hear a case that involves such "egregious" conduct by police. Tarricone said Duncan deviated from his training and from Framingham Police Department protocol during the raid — factors that should be weighed in determining whether his actions were reasonable.

“These are rules that were designed to prevent this from happening, and either from sheer incompetence or willful decision not to abide by them, Duncan did not abide by them, and that constitutes excessive force,” he said.

Stamps was killed Jan. 5, 2011, inside his first-floor apartment at 26 Fountain St., where the retired MBTA maintenance worker and grandfather of 12 lived with his wife and stepson. Police were granted a warrant to search the apartment after receiving a report that the stepson, Joseph Bushfan, and others were selling crack cocaine from the home.

After breaking down the front door and rushing into the apartment, two officers ordered Stamps to get on the floor when they encountered him in a hallway. He complied, placing his hands near his head. While the officers left to continue searching the apartment, Duncan - one of 11 officers involved in the operation - approached, stood over and pointed an M4 rifle at Stamps, ultimately firing a shot that struck Stamps in the head, killing him.

In 2011, the Middlesex District Attorney's Office investigated the shooting and ruled it was accidental, and that no criminal charges were warranted. Stamps’ wife Norma Stamps and his son, Eurie Stamps Jr., then filed a civil lawsuit against Duncan and the town in 2012.

In its appeal, the town argues it was not unreasonable for Duncan to point his weapon at Eurie Stamps, given the "rapidly evolving circumstances" that can exist in any drug search. In this case, detectives believed three men in the apartment had affiliations to Boston gangs, and had criminal histories including assault and armed robbery, according to a brief filed by the town.

"This was a tense situation and the officers had to be on high alert,” the brief reads. “There was no telling what any occupant of the apartment would do given the stakes involved."

The American Civil Liberties Union filed a court brief in September attacking the town’s defense, arguing that an officer who unreasonably aims a rifle at someone’s head has clearly violated established law. Adriana Lafaille, an attorney with ACLU of Massachusetts, said the Stamps case is important not only because an innocent man died, but also because it comes at a time when families across America are increasingly being subjected to “highly militarized police forces” entering their homes to carry out routine drug searches.

“It’s very important that we understand that when police put the lives of ordinary citizens at risk, that there can be consequences for that, and that they’re not going to be able to claim immunity simply because what happened is an accident,” Lafaille said.

Jim Haddadin can be reached at 617-863-7144 or jhaddadin@wickedlocal.com. Follow him on Twitter: @JimHaddadin.