Witnesses will testify on a woman screaming, gunshots, and that lights were on at athlete Pistorius's home the morning his girlfriend Reeva Steenkamp was shot, the Pretoria Magistrate's Court heard.

"After he heard gunshots, he saw the lights were on," said investigating officer Hilton Botha of a witnesses account he intended bringing to court.

"Then he heard a female screaming and he heard another couple of gunshots," continued Botha.

"I believe he knew she was in the bathroom and he shot four shots in the bathroom and killed her," Botha testified.

He was responding to questions from prosecutor Gerrie Nel, who is opposing an application for bail by Pistorius.

He said in an affidavit read to the court on Tuesday that he thought an intruder was in the house when he fired the shots into the bathroom, which killed Steenkamp.

In an affidavit on Tuesday, Pistorius told the court he thought he was firing shots at an intruder in the bathroom.

Steenkamp was shot dead early on February 14 at Pistorius' home in Pretoria.