During his testimony on Tuesday, Christiaan Oldewage told the court he was not the monster people perceived him to be. He denied ever assaulting his stepson Stiaan and his wife Juanita.
"The baby was okay. He was a very good baby. He never cried a lot. I didn't assault the baby under any circumstances. It is ridiculous to say that I did," he said.
He could not explain how Stiaan sustained a fractured skull, 16 rib fractures, and multiple internal injuries which led to his death on 13 December 2011.
He claimed that he believed the scratches on the baby's body were caused by a cat.
He said the boy could have been allergic to the cat, thus that caused the severe swelling he had around the lips and eyes.
A doctor who testified in the trial said the baby was blue and not breathing when he was admitted to hospital.
He said he had never seen such serious injuries, even in victims of car accidents.
Oldewage's wife Juanita was arrested with him, but committed suicide in August this year.