Oscar Pistorius cried and prayed as Reeva Steenkamp lay dying in his home, the High Court in Pretoria heard on Thursday.

"Oscar was crying, saying please let her live," radiologist Johan Stipp said to questioning from prosecutor Gerrie Nel.

"He was saying he would dedicate his life to God if she will only live."

Stipp, who was woken by screaming and subsequently heard gunshots, described how he drove to Pistorius's home nearby and found Steenkamp on the floor at the bottom of the stairs on the ground floor.

Nel asked him to look at pictures in a file in front of him. The images were not shown on the television screens in court.

Stipp, who told the court he was a doctor, rubbed his chin as he looked at the photos and confirmed that they were of the woman as he found her lying in the house.

He said he knelt down beside her.

"I tried to open her airway and look for any signs of life. She had no pulse in her neck and no peripheral pulse."

He said Pistorius was kneeling next to her, two of his fingers in her mouth, trying to open her airway.

"She was clenching down on Oscar's fingers," said Stipp.

"I opened her right eyelid. Her pupil was fixed, dilated and her cornea was already drying out. To me it was obvious that she was dying."

"I noticed blood in her hair and brain tissue mingled with that."

As Pistorius listened to this he bent over in the dock, his hands pressed against the back of his head.

Court adjourned for lunch at 12.50pm.

Pistorius is accused of the murder of Steenkamp. He is also charged with illegal possession of a firearm and ammunition, and two counts of discharging a firearm in public.

He allegedly fired a shot from a Glock pistol under a table at a Johannesburg restaurant in January 2013.

In September 2010 he allegedly shot through the open sunroof of a car with his 9mm pistol while driving with friends in Modderfontein.