Gerrie Nel, one of South Africa's top attorneys, said it was beyond belief that Reeva Steenkamp would have remained silent in the cubicle with an armed Oscar Pistorius shouting and screaming in the adjoining bathroom.
The prosecution alleges the 29-year-old model took refuge in the toilet during an angry row with the athlete, and he then shot her through the door.
Oscar Pistorius, who says he fired at what he thought was an intruder, has testified that Steenkamp did not cry out during the incident in the early hours of Feb. 14, 2013.
However, under withering cross-examination from Nel - known in South Africa as "The Pitbull" - the 27-year-old track star was forced to concede he could not have heard whether she screamed or not because his ears were ringing from the sound of gunfire.
People living nearby have testified to hearing a woman's terrified screams before and during a volley of shots.
"She's awake. She's in the toilet. You're shouting. You're screaming. You're three metres from her. She would have responded. She would not have been quiet, Mr Oscar Pistorius," Nel said.
"She didn't respond, my Lady," an apparently distressed Pistorius replied, addressing judge Thokozile Masipa.
"Did she scream at all whilst you shot her four times" Nel continued.
"No, my Lady."
"Are you sure Are you sure, Mr Pistorius, that Reeva did not scream after the first shot" Nel continued. "Are you, Mr Pistorius"
After a brief silence, Oscar Pistorius said: "My Lady, I wish she had let me know she was there."
"After you fired the first shot, did she scream" Nel asked.
"No, my Lady."
"Are you sure Would you have heard her"
"I don't think I would have heard her."
"Exactly," Nel said.
"A gunshot went off. My ears were ringing," Oscar Pistorius said.
"How can you exclude the fact she was screaming if you couldn't hear" Nel asked.
Oscar Pistorius then conceded: "My Lady, the sound of that gunshot in the bathroom, you wouldn't have heard anyone scream. The decibels of the gunshot, I don't believe you would have heard anyone scream. When I had finished firing the gunshots, I was screaming and I couldn't hear my own voice."
Nels followed up with his central accusation - that the couple had an argument and Steenkamp fled to the toilet pursued by Oscar Pistorius, who shot her through the locked door.
Steenkamp was hit by three of the four 9 mm hollow-point rounds Oscar Pistorius fired. A police ballistics expert has testified that the first round hit her hip and the final one her head, killing her almost instantly.
"You knew that Reeva went behind the door and you shot at her," Nel said.
"You shot at her knowing she was behind the door."
Oscar Pistorius, who faces life in prison if convicted of murder, denied it, his voice wavering with emotion, before the court adjourned until Monday.
The trial, now 21 days old, has gripped South Africa and millions of sports and athletics fans around the world who have seen Pistorius as a symbol of triumph over physical adversity.
His disabled lower legs were amputated as a baby but, running on carbon fibre prosthetic limbs, he went on to achieve global fame as the "fastest man on no legs", winning numerous Paralympic gold medals and reaching the semi-finals of the 400 metres in the 2012 London Olympics against able-bodied athletes.