A Dorchester gang member was convicted today of trying to murder a one-time friend, shooting him in the back and paralyzing him for renouncing gang life, Suffolk County District Attorney Daniel F. Conley said.

A Suffolk Superior Court jury found DONALD RAY WILLIAMS (D.O.B. 10/4/84), a.k.a. “MANN,” guilty of armed assault with intent to murder, aggravated assault and battery with a dangerous weapon, unlawful possession of a firearm, unlawful possession of ammunition, and unlawfully carrying a loaded firearm. The attack left the victim with injuries that will require him to use a wheelchair for the rest of his life.

Williams, who is currently serving eight to nine years in prison for a different shooting, faces up to 20 years on the lead charge when he is sentenced tomorrow.

“This case could mark a turning point in our city,” Conley said. “We reached this result because the victim, a former gang member, had the courage to testify in court against the man who tried to kill him. He put violence and retaliation behind him and found true justice under the law. And even though he never left his wheelchair, he stood taller than anyone else in that courtroom.”

Testimony began April 11. Lawyers gave closing arguments yesterday morning. Jurors deliberated for about a day and a half.

“The jury deserves credit for its work on this case,” Conley said. “They gave it their full attention and they reached a just verdict.”

Assistant District Attorneys Gretchen Lundgren and Melissa Brooks introduced evidence and testimony proving that the victim, then 20, had been a member of the Greenwood Street Packers, the street gang Williams led. On the night of Nov. 23, 2007, the victim testified, he met with members of that gang and told them he was giving up gang life.

The victim returned the handgun Williams had given him and bought his friends a meal as he prepared to give up the life they had shared. In the early morning hours of Nov. 24, they drove him to his girlfriend’s home on Torrey Street in a two-car caravan.

As the unarmed man walked toward that residence, the evidence showed, Williams got out of one vehicle, walked up behind him, and fired three shots into his back. The victim fell to the ground and turned to face the man who had once been his best friend.

“Bitch-ass [expletive],” Williams said, pulling the trigger again and shooting the man in the face. “That’s what you get.”

“It was a cowardly act,” Conley said. “He knew the victim had given up his gun and posed no threat to him, his friends, or anyone else.”

Grievously wounded and unable to use his legs because his spinal cord had been damaged, the victim saw his cell phone where it had fallen a few feet away. After Williams and the other men drove away, the victim crawled to the phone, replaced the battery that had fallen out, and called his girlfriend’s sister.

The victim told the young woman that he had been shot, that he was about to die, and that she should tell his brother that “Mann” shot him. No one else, he testified, would have believed her because he and Williams had been so close.

Emergency medical personnel raced him to Boston Medical Center, where he underwent emergency surgery and remained in an induced coma for weeks. He identified Williams as his shooter to first responders, to police at the hospital, to the Suffolk County Grand Jury, and, last week, to a packed courtroom.

No other members of the Greenwood Street Packers testified. Two who were subpoenaed refused to take the stand and the court ruled that both had Fifth Amendment privileges.

Jennifer Stott was the DA’s assigned victim-witness advocate. Rosemary Scappicchio represented the defendant. Judge Frank Gaziano will sentence him tomorrow at 11:00 a.m. in courtroom 906 of Suffolk Superior Court.