NEW YORK (Reuters) - The New York City medical examiner who conducted an autopsy on an unarmed black man who was killed during a 2014 arrest said at a hearing on Wednesday that a police officer’s chokehold set off a “lethal cascade” of events that ended in the man’s death.

FILE PHOTO - A small crowd of protesters rally for the disciplinary trial of Police officer Daniel Pantaleo in relation to the death of Eric Garner at 1 Police Plaza in the Manhattan borough of New York, New York, U.S., May 13, 2019. REUTERS/David 'Dee' Delgado

Cellphone videos taken by bystanders show Officer Daniel Pantaleo putting his arm around the neck of Eric Garner to subdue and arrest him on suspicion of selling loose cigarettes on a sidewalk of the city’s Staten Island borough.

The New York Police Department (NYPD) is conducting a disciplinary trial for Pantaleo that could lead to his dismissal, nearly five years after Garner’s death. The department has banned officers from using chokeholds for decades, saying the maneuver is too risky.

“In my opinion, that’s a chokehold,” Dr. Floriana Persechino, the medical examiner, said after video footage of the arrest was put on pause during the hearing. She said the chokehold would have been painful and constricted Garner’s airways, triggering “a lethal cascade of events” that led to his death.

Video of the arrest sparked a national outcry over policing tactics used against black men. Garner’s dying refrain of “I can’t breathe!” became a rallying cry in the early days of the Black Lives Matter movement.

Using a green laser pointer, Persechino explained that the autopsy photographs showed a band of ruptured blood vessels in the muscles in the front of Garner’s neck, and said they were caused by pressure from Pantaleo’s forearm.

In hearings this week at the NYPD’s headquarters in Manhattan, prosecutors from the Civilian Complaint Review Board, an independent city agency with oversight powers over the NYPD, have said that Pantaleo should be fired.

CHOKEHOLD AND “CONTRIBUTING CONDITIONS”

Pantaleo’s lawyers have argued that he did not use a chokehold, but instead used an authorized “seatbelt” hold that slipped as Garner struggled, and said that the officer did not cause Garner’s death.

Persechino agreed with one of Pantaleo’s lawyers, Stuart London, that the chokehold was not the sole cause of death.

A summary of her findings shared with reporters in 2014 and repeated in Wednesday’s hearing ruled that the cause of death was: “Compression of neck (choke hold), compression of chest and prone positioning during physical restraint by police.”

It also said that Garner’s asthma, obesity and high blood pressure were “contributing conditions.” Garner was 43 when he died.

London, Pantaleo’s lawyer, tore up a copy of that report at an earlier hearing, saying it was wrong and that Garner caused his own death in part by resisting arrest despite being in poor health.

London sought to undermine the medical examiner’s ruling on Wednesday by noting that Persechino found no external abrasions on Garner’s neck and that small bones and cartilage in his neck were not fractured.

Persechino said forearms, being soft and broad, often do not leave external marks in a chokehold, and that she saw fractured neck bones or cartilage in only a minority of choking and strangling cases.

In this week’s hearings, several of Pantaleo’s colleagues, including investigators in the police department’s Internal Affairs Bureau and an officer who oversees cadet training, say the videos show Pantaleo used a chokehold.

Pantaleo, who has been assigned to a desk job since Garner’s death, has sat silently by his lawyers during the hearings, dressed in a dark suit.

An NYPD judge overseeing the hearing will make a ruling at the trial’s end, but the ultimate decision about Pantaleo’s fate will be made by Police Commissioner James O’Neill.