The murder trial of paralympic athlete Oscar Pistorius enters day 24 in the High Court in Pretoria on Wednesday, with a former senior police forensic expert continuing his evidence.

Pistorius ended his seventh day in the witness stand on Tuesday. He maintained he was innocent and had acted involuntarily when he fired the shots that killed his girlfriend Reeva Steenkamp.

Barry Roux, SC, for Pistorius, called former police forensic expert, Roger Dixon.

Dixon said he had conducted sound and vision tests that contradicted testimony from Pistorius's neighbours, who told the court they heard a woman's screams followed by gunshots.

He agreed with Pistorius's defence that police investigators had possibly compromised evidence, telling the court it was clear that one had stepped on the door. He termed this "most unprofessional".

Wrapping up his cross-examination earlier on Tuesday, prosecutor Gerrie Nel said Steenkamp had run to the bathroom following an argument with Pistorius.

Nel said Pistorius was lying and had killed his girlfriend in cold blood, but failed to win a concession from him that he had intended to fire his 9mm pistol.

Pistorius is charged with murdering Steenkamp during an argument. He shot her through the locked door of his toilet on February 14 last year, saying later he mistook her for an intruder.

On Monday, the State asked for the trial to be adjourned to May 5 and Judge Thokozile Masipa is due to rule on that on Wednesday.

Pistorius is also charged with three contraventions of the Firearms Control Act, one of illegal possession of ammunition and two of discharging a firearm in public.

Pistorius has also denied guilt on these three charges.