Devante Spencer is behind bars for the murder of Rochester teen activist, Lawrence Richardson in April of 2012. While in prison at Attica, prosecutors said Spencer and two other inmates attacked another inmate, severely cutting the victim's face, leaving a disfiguring scar. The jury handed out a guilty verdict this week.

The Rochester man serving a life sentence for the murder of a teen activist in Rochester has been convicted on new charge.

Wyoming County prosecutors say a jury took just 20 minutes to deliberate before issuing a guilty verdict against Devante Spencer.

He is behind bars for the murder of Lawrence Richardson in April of 2012. Richardson, a teen empowerment advocate, was shot and killed by Spencer on Dayton Street.

While in prison at Attica, prosecutors said Spencer and two other inmates attacked another inmate, severely cutting the victim's face, leaving a disfiguring scar.

“I am grateful that the jury understood that the victim, himself a convicted criminal, deserved to be treated like any other victim. He did not deserve to be attacked," wrote Wyoming County Special District Attorney Michael J. Flaherty, Jr. in a statement.

Flaherty says he plans to ask the judge to sentence Spencer as a persistent violent felony offender -- which would be considered if he ever applied for parole.