"I deny the allegation in the strongest terms. Nothing can be further from the truth," an affidavit read out to the Pretoria Magistrate's Court by Pistorius's lawyer advocate Barry Roux said.
Pistorius is accused of murdering his girlfriend Reeva Steenkamp on the morning of Valentine's Day.
Prosecutors accuse the athletics star of premeditated murder and told the court that he shot Ms Steenkamp dead by firing through a bathroom door.
Prosecutor Gerrie Nel told the court that Mr Pistorius had got up from bed, put on his prostheses, and fired his gun through the door of the small bathroom.
He shot four times and hit Ms Steenkamp three times.
Mr Nel added that the defendant later broke down the bathroom door and carried the body downstairs.
Pistorius responded by saying the couple had decided to spend that evening at home. They were in the bedroom when at one point Mr Pistorius went to the balcony and heard a noise.
"It was pitch-dark in the bedroom," the affidavit said. "I did not have my prosthetic legs on and felt extremely vulnerable."
Mr Pistorius thought Ms Steenkamp was still in bed and he fired through the bathroom door believing he was shooting at an intruder.
When he realised Ms Steenkamp was not in the bed, "it filled me with horror and fear", the affidavit said.
Mr Pistorius broke the door down with a cricket bat to find his girlfriend shot inside.
Tuesday's hearing – on the same day as family held a private funeral for Steenkamp - was later adjourned until Wednesday.
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