NEW YORK (CBSNewYork) -- The departmental trial has begun for NYPD Officer Daniel Pantaleo.
He's accused of using a chokehold on Eric Garner, who later died on Staten Island in 2014.
The case is being prosecuted by the Civilian Complaint Review Board, reported CBS2's Jenna DeAngelis.
Monday was the first day of the trial. If Pantaleo is found to have violated department rules, he could be fired.
Eric Garner's mother held an umbrella to shield her from the rain, which matched her mood, as she walked into police headquarters.
"I feel like the weather, dreary," Gwenn Carr said.
Nearly five years after her son's death, the departmental disciplinary trial began for Pantaleo, who is accused of using a banned chokehold on Garner while attempting to arrest him for selling loose cigarettes.
He's been on desk duty since the 2014 incident. This trial is the start of deciding his future with the NYPD.
"We are just looking for justice and we hope that the departmental trial proves to be in our favor," Carr said.
"I'll settle him for him losing his job, losing his pension and being held accountable for what he did," another person attending the trial told DeAngelis.
The New York City Civilian Complain Review Board, a police oversight agency, is prosecuting Pantaleo.
If he is found to have violated department rules regarding the reckless and intentional use of a chokehold he could be fired. The police commissioner could apply punishment from loss of vacation days all the way through to termination. The trial is expected to last about two weeks.
Pantaleo's attorney remained positive heading into the trial.
"Always optimistic," attorney Stuart London said.
Video of the incident has become the centerpiece of the case against Pantaleo.
The city's medical examiner ruled Garner's death a homicide, saying he died from a choke hold complicated by health issues. But just last month, the attorney for officer Pantaleo announced the NYPD's chief surgeon determined he did not use a chokehold when trying to arrest Garner.
The trial began with opening arguments at around 10 a.m. before Deputy Commissioner for Trials Rosemarie Maldonado.
The packed trial room has seating capacity for about 60 people, and extra chairs were added.
"The words 'I can't breathe' tells you who causes his death. Daniel Pantaleo used a prohibited chokehold," said attorney Jonathan Fogel for the CCRB. "He gave his victim a death sentence over loose cigarettes."
Fogel said Pantaleo applied pressure on Garner's neck for 15 seconds, calling it a "lethal dose of deadly force."
"A chokehold set off a domino effect that led to cardiac arrest that led to his death," Fogel added. "It is an outrage that Eric Garner is not alive today. He was given a death sentence for loosies."
Pantaleo's attorney then offered his version of the incident.
"I'm tired of it. It stops today and it's done," London said, repeating words Garner said to responding officers as he was being arrested. London said that was the beginning of Garner resisting arrest.
London said Pantaleo exercised tremendous restraint, and that there was more than 10 minutes before any officer put a hand on Garner. London said Pantaleo didn't use a chokehold, but an academy-taught "seatbelt technique," a takedown that was misrepresented in the autopsy report as a chokehold. He said Garner's chronic asthma made him a "ticking time bomb" who set things in motion by resisting arrest.
"Had he accepted the summons, he would be here today," London said.
London said Garner jerked Pantaleo towards a plate glass window, and disputed what happened when Garner was on the ground.
"He was not squeezing his neck. He was trying to control him to cuff him," London said. "There's no evidence he was applying pressure to his neck."
London said the fact that Garner was saying "I can't breathe" shows he wasn't choked because he was speaking.
Ramsey Orta, the man who took the cell phone video, testified via video link from prison. Orta is serving time after pleading guilty to possession of a gun and criminal sale of a controlled substance. Orta testified there was a fight moments before the video began that Garner had broken up, and that's when police arrived.
Garner's mother and sister sobbed openly in court as the video was played.
On Monday morning, a man stood holding an image from that video, and protesters blocked the FDR with their own signs reading "#FirePantaleo."
Before walking inside, Garner's sister had a message for Pantaleo.
"Do the right thing," Elisha Flagg-Garner said.
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