After just three days of witness testimony, prosecutors in the disciplinary trial of police officer Daniel Pantaleo have rested their case.

The prosecution’s last witness was a veteran city pathologist who examined Eric Garner’s body and testified Wednesday that a police chokehold and takedown set off the chain of events that led to the 43-year-old, unarmed man’s death.

The altercation happened nearly five years ago on Staten Island, when Pantaleo and other officersolice were trying to arrest Garner for allegedly selling untaxed cigarettes. Graphic cell phone video of Garner’s final moments sparked a sustained outrage and became a rallying cry for the Black Lives Matter movement.

Dr. Floriana Persechino, a senior forensic pathologist in the office of the Chief Medical Examiner, said the chokehold compressed Garner’s airway, making it difficult for him to breathe and possibly triggering an asthma attack.

She also blamed his death on chest compression and the position police held him in—face down on the sidewalk while they handcuffed his hands behind his back. Persechino said Garner’s poor health were contributing factors.

She said she examined the body for many hours after the confrontation that touched off nationwide protests against police brutality.

Pantaleo’s attorneys have blamed the death on Garner’s health issues, including chronic asthma, high blood pressure and obesity. But Persechino, watching the video from the witness stand in a trial room at police headquarters, identified what Pantaleo did as a chokehold and called it an initial, significant factor in a cascade of events that killed him.

The medical testimony is considered crucial to proving whether Pantaleo’s actions rise to the level of criminal attempted assault. Pantaleo’s lawyers plan to call their own expert witnesses to refute the results of the autopsy later in the trial.

Garner’s mother, Gwen Carr, sat in the front row of the tense trial room while the doctor testified. Carr was surrounded by the mothers of other men who died in confrontations with police. She left when the judge warned that the autopsy photos would be explicit.

Stuart London challenged Persechino and got her to acknowledge that Pantaleo did not die of a chokehold in and of itself. He also questioned why there was no damage to Garner’s trachea, larynx or a bone called the hyoid.

Persechino said that it’s not uncommon for the hyoid bone to stay intact and said the fat around Garner’s neck may have allowed a degree protection. She did find significant hemorrhaging around the muscles of Garner’s neck.

Thursday, the defense plans to call several police officers to testify.

Cindy Rodriguez is an investigative reporter for New York Public Radio. You can follow her on Twitter at @cynrod.