NEW YORK (CBSNewYork/AP) — An undercover New York City police detective accused of taking part in a motorcyclists-versus-driver melee is now on trial, and the victim of the attack testified Monday.

Detective Wojciech Braszczok faces top-level assault charges in the September 2013 attack on a sport-utility vehicle driver while he was off-duty.

As CBS2’s Alice Gainer reported, Braszczok covered his face with a sweatshirt as he entered the courtroom on Monday.

Assistant District Attorney Josh Steinglass said Monday that Braszczok and a co-defendant took part in the violence because the victim wouldn’t yield to “hordes of bikers.”

The SUV driver, Alexian Lien, was with his wife and daughter at the time of the attack, which was captured on a video camera mounted on a biker’s helmet. He was taken to the hospital for stitches to his face, and was also injured on the hands and torso.

One of the bikers was seriously injured when the driver hit the gas to get away and ran him over.

Alexian Lien, the man who was attacked by a group of bikers in Washington Heights in 2013, testifies at the trial of one of the alleged assailants

Alexian Lien, the man who was attacked by a group of bikers in Washington Heights in 2013, testifies at the trial of one of the alleged assailants

Lien testified Monday that the bikers harassed drivers and popped wheelies starting far downtown. Lien said his wife threw plums and a water bottle to shoo away the bikers.

Lien said he was growing scared, and he turned to his wife and said, “What do I do?” He said she told him, “Just go.”

Panicked, Lien said he knew he hit someone, but feared for his family’s lives.

It was once he drove up to Washington Heights that he was pulled out of his SUV and beaten.

As TV 10/55’s Weijia Jiang reported, prosecutors presented pictures of Lien, his face swollen, his body covered in bloody cuts and bruises.

The Manhattan District Attorney’s office called the attack “classic mob mentality.” But the defense countered that Lien did nothing to defuse the situation.

When asked why he did not just pull over, Lien said: “That’s a very good question. I was very focused on enjoying the day I planned for my wife and my daughter and myself; didn’t feel the need to pull over.”

The defense also asked about Braszczok, and asked Lien whether he could attribute any aggressive physical contact to the detective personally. Lien said no.

But prosecutors said Braszczok failed to do what an NYPD officer is supposed to do in such a situation, by reporting the crime or intervening if possible. To which his defense attorney said that though it was not Braszczok’s proudest moment, it did not make him a criminal.

A judge will determine the case. Braszczok has been suspended.

Eleven men were indicted after the melee. The others have pleaded guilty to charges including assault and riot. One of the bikers was sentenced earlier this month to a year in prison.

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Defense attorney John Arlia says his client was acting as a policeman who had just seen an SUV crush a biker. He says his client did not go on the attack.

Prosecutors say Braszczok shattered the SUV’s back window, as well as doing nothing to end the assault or get help.

“Imagine the rage,” Steinglass said.

Braszczok’s lawyers, however, have said he never came close to the SUV driver and that the video footage will exonerate him.

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