Days after Naadir Abdul-Ali's girlfriend left him, prosecutors said, he told her "if we can't be together someone's got to go."
Hours later, they said, the woman's father was shot to death in his Lower Moreland Township home.
Abdul-Ali, 21, of Philadelphia, described as a heavyweight boxer, was an "extremely controlling, paranoid, abusive, and vengeful man," Deputy District Attorney Thomas McGoldrick told a Montgomery County Court jury Wednesday in opening arguments at Abdul-Ali's murder trial.
Abdul-Ali and two of his friends, Abdurrahman Amin and Desmond Smith, are charged with breaking into Kevin Brown's home in September and shooting him to death.
A fourth man, Mujahid Mathews, also was charged but pleaded guilty to third-degree murder and is expected to testify against the others.
But the attorney for Smith, S. Philip Steinberg, said he will call witnesses who will say that Smith, 21, also of Philadelphia, was with his girlfriend the night of the murder.
Steinberg said he will present video footage that shows Smith was on SEPTA's Market-Frankford line that night and therefore nowhere near in Lower Moreland.
"You'll wish when you get a verdict sheet you could write Desmond Smith is innocent" instead of "not guilty," the term used in court, Steinberg told the jury Wednesday.
The three men's trials, before Judge Thomas P. Rogers, have been consolidated into one that is expected to last two weeks.
McGoldrick said that Abdul-Ali's ex-girlfriend - the victim's daughter - was raped and beaten before leaving him and returning to her parent's home in Lower Moreland days before the killing.
Prosecutors said Abdul-Ali used his grandmother's car that night to drive to the family's home with the three other men, break in, and kill Brown.