A Plymouth Township man showed no emotion as a Montgomery County Court judge pronounced him guilty this morning of first-degree murder in the death of 14-year-old Ebony Dorsey.

Mark Patrick O'Donnell was also found guilty of involuntary deviate sexual intercourse.

Judge William J. Furber also found O'Donnell, 48, guilty of tampering with evidence and abusing a corpse in connection with the fatal strangulation of Dorsey on Dec. 7. The case will now move to the death penalty phase.

During a break after the verdict in the non-jury trial, O'Donnell's mother cried quietly in her seat. The victim's father, Evan Dorsey, stood and hugged half a dozen detectives and police officers.

Upon returning to the packed courtroom, the judge said the penalty phase would begin at 11 a.m.

The victim's mother, Danielle Cattie, 34, of Whitpain Township, who had been nervously rocking back and forth in her seat, said she felt "unbelievable relief."

Cattie, O'Donnell's former girlfriend, spent the night before the murder doing drugs with O'Donnell while her daughter baby-sat for O'Donnell's 4-year-old daughter.

The homicide occurred when O'Donnell returned to his home to pick the teen up so that she could go to school. She was an honors student at Wissahickon High.

Contact staff writer Kathleen Brady Shea at 610-701-7625 or kbrady@phillynews.com.