Orlando Williams
Orlando Williams will spend his life behind bars after murdering his fiance's eight-year-old son. Allegheny County Jail

A Pittsburgh man will spend the rest of his life in jail, without the possibility of parole, after he was found guilty of killing his fiance's eight-year-old son.

Orlando Williams, was charged with homicide and endangering a child in June 2016 after the boy suffered severe head trauma. Williams, 39, slammed the boy onto the floor because his room was not clean.

Williams had tripped on a washing basket and, out of anger, attempted to throw the eight-year-old onto a bed, but missed and "slammed" the boy onto the floor. He yelled three times for the boy to get up, but there was no response. He had spent the afternoon drinking at Ohiopyle State Park, a local outdoor camping and recreation ground.

Williams carried the boy downstairs and left him in a living room chair overnight. The next morning, Williams and the boy's mother took him to a hospital where he was rushed into intensive care. He was found to have suffered a "herniated brain stem" and the coroner later ruled his death homicide.

He was found guilty of first-degree murder and endangering a child earlier in December.

Williams was also found to have beaten the boy, who he punched so hard in the chest that it bruised, for not taking the rubbish out the correct door.

The boy's mother, Aliehsa Lininger, testified against Williams in court. She was charged with endangering a child and faces court later in December.

According to Williams' defense attorney, he was a "father figure" to his fiance's boy and he was "inconsolable" after the events. The defense attorney said based on the evidence, Williams should only have been convicted of involuntary manslaughter.

Allegheny County Common Pleas judge Donna Jo McDaniel the decision depended on if Williams killed with "specific intent". "I find beyond reasonable doubt the answer is yes," McDaniel said according to the Pittsburgh Post-Gazette.