Christopher Wall has been convicted of battering Hayley Wall - who was his niece as well as his partner - and was due to be sentenced on Friday.
Miss Wall died in hospital in December last year, nine days after she was found wandering around outside a supermarket with serious head injuries.
Before the 25-year-old slipped out of consciousness she was able to tell emergency crews her name and address. She also told one of the paramedics who attended to her: "My partner smashed a TV over the top of my head."
When police visited her home they found signs of a disturbance on the second floor including a door on the landing that was knocked off its frame with two long dark hairs embedded in a crack halfway up the door with a number of blood spots.
Officers also found a large flat-screen TV at the bottom of the stairs leading to the second floor that appeared