Oscar Pistorius leaves the high court in Pretoria on Tuesday, March 18, 2014. Picture: THEMBA HADEBE

Johannesburg - Ballistic expert Captain Christian Mangena is expected to testify on Wednesday whether Oscar Pistorius was without his prosthetic legs when he fired shots that killed his girlfriend, Reeva Steenkamp.

Taking the stand on Tuesday, Mangena told the North Gauteng High Court in Pretoria he had performed tests linking the holes in the toilet door through which the athlete fired his handgun with marks on the tiles, and the position of Steenkamp's fatal wounds.

The one bullet that missed Steenkamp was fired at a downward angle of five to six degrees, Mangena said, adding that he had used laser technology to back up conventional ballistic tests.

After questioning Mangena at length about his methods and the results of his measurements, prosecutor Gerrie Nel said he would prefer to leave questions as to his conclusions for Thursday.

Mangena, the fourth police expert, followed colleagues who were vigorously cross-examined by Pistorius's lawyer, Barry Roux, as he seeks to make a case that police failed to preserve the scene of the shooting and tampered with evidence.

Pistorius has been charged with the premeditated murder of Steenkamp in his house on February 14 last year, but contends that he mistook her for an intruder.

He has also denied two charges of contravening the Firearms Control Act.