Circuit Judge Hamilton, writing for the panel, ruled that José Cartagena's conviction for allegedly pistol-whipping 17-year-old Calep Carvajal during a November 2014 arrest must be set aside. The court affirmed Cartagena's three remaining convictions.

The case centered on the testimony of Dr. Yocasta Brugal, who examined Carvajal after four officers from a Puerto Rico drug unit allegedly assaulted him during and after his arrest. Carvajal never testified at trial because prosecutors were unable to locate him. Instead, Dr. Brugal relayed his account to the jury.

"Critical here, Dr. Brugal testified that Carvajal told her the cause of his head wound," Hamilton wrote, noting the doctor told jurors that Carvajal said "he received a trauma on his head that he identified had been produced by the butt of a revolver."

The government argued that Carvajal's statement was offered for "context" rather than for its truth. Hamilton rejected that distinction. "Carvajal's statement could have helped the jury evaluate Dr. Brugal's opinions only if it were true," the court explained.

The panel found the error was not harmless. Dr. Brugal was "easily the most trustworthy witness who testified against Cartagena" on the pistol-whipping charge, the court said. The longtime medical school dean had handled over fifteen thousand forensic cases, while other government witnesses had what the court described as serious credibility problems.

The court affirmed Cartagena's convictions for punching Carvajal in a squad car, filing a false police report, and obstructing justice by lying to prosecutors. According to the court's recitation of the underlying facts, Officer Nieves shot Carvajal in the back as he fled on a bicycle, and Cartagena then tackled and handcuffed him and allegedly pistol-whipped him in the back of the head while he lay on the ground unarmed. Three other officers had pleaded guilty; Cartagena went to trial and was convicted on all four counts.