Pretoria - Oscar Pistorius's lawyer Barry Roux, SC, on Friday questioned the first police officer on the scene of Reeva Steenkamp's murder on the reliability of photos taken at the crime scene in February last year.

“When can we rely on the scene photo as a true reflection, and when is it changed?” Roux asked former police colonel Giliam van Rensburg during cross-examination in Pistorius's murder trial in the High Court in Pretoria.

He was referring to a photo displayed in court showing a white cellphone on the tiled floor of Pistorius's bathroom, along with a section of grey towel and a toilet door panel.

Van Rensburg conceded that when he arrived at the house the towel covered the phone. He launched into a lengthy explanation of how the first photos taken of a crime scene were the most important and showed the scene unchanged.

More photos were then taken later as police “investigated further”.

Van Rensburg has since resigned from the police to coach sport.

Pistorius claims he shot Steenkamp through the locked door of his toilet cubicle thinking she was an intruder. He bashed open the door with a cricket bat and carried her bleeding, lifeless body downstairs.

Pistorius is accused of the premeditated murder of model and law graduate Steenkamp. He is also charged with illegal possession of 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. On September 30, 2012 he allegedly fired a shot from his 9mm pistol through the open sunroof of a car while driving with friends in Modderfontein.

Sapa