A photograph of Oscar Pistorius's blood-stained prosthetic legs was used by his chief defence lawyer Thursday to attempt to show that the athlete was wearing them, as he says, when he broke down a toilet door with a cricket bat to get to the girlfriend he fatally shot.

The image, showing the prosthetic limbs with white socks and stained with Reeva Steenkamp's blood up to the knee, was displayed by lawyer Barry Roux on a TV monitor at Pistorius's murder trial.

Roux was trying to reinforce the Olympian's story that he shot the model by mistake on Valentine's Day last year and then desperately broke through a locked toilet door to help her.

The prosecution has attempted to cast doubt on parts of Pistorius's story, including, specifically, that he was wearing his legs when he broke through the toilet door with his bat.

Prosecutors show 'trail of blood'

Later on Thursday, prosecutors displayed a sequence of photos showing the blood stains found on the floors, walls, stairs and chairs in the athlete's house after he fatally shot his girlfriend.

In one photograph displayed on TV monitors at Pistorius' murder trial, spots of blood are seen right next to some the double-amputee Olympian and multiple Paralympic champion's golden trophies.

The TV screen next to Pistorius was switched off during the display.

Former police colonel Schoombie van Rensburg, one of the first officers on the scene, described finding a "trail of blood" in Pistorius' bedroom. 

Roux cross-examined a police forensics expert for a second day in the Pretoria courtroom, and also challenged Col. J.G. Vermeulen's analysis of a bullet-marked toilet door that was removed from the bathroom at Pistorius's home, where the double amputee killed the 29-year-old Steenkamp before dawn on Feb. 14, 2013.

Pistorius, 27, has said he shot Steenkamp by mistake through the door, fearing there was a dangerous intruder in the house. The prosecution says he intentionally killed her after an argument. The celebrated runner faces a possible life sentence in prison if convicted. He has pleaded not guilty to charges of murder and three firearm-related offences.

Minutely scrutinizing almost every aspect of the police investigation, Roux asked why missing wooden fragments from the door weren't examined, why Pistorius's story wasn't seriously considered and tested by the police expert, and why there wasn't detailed microscopic analysis of the door and any fabrics on it.

Roux said the defence had evidence of a sock fabric embedded in the wood of the door which would show, as Pistorius says, he tried to kick through it wearing his prosthetics. The forensic investigation for Pistorius was done by Vermeulen's former commanding officer, Roux said.

Do you know him, Roux asked Vermeulen. Vermeulen said the man used to be his commanding officer and he knew him to be "competent."

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Defence lawyer Barry Roux questioned how police collected evidence related to the Pistorius case, and suggested some investigators approached their work with a bias. (Theana Breugem/Reuters)

Roux also showed a photo of a part of the door which he said showed a mark one of Pistorius' prosthetics had made when he kicked it.

"If that is a mark of a prosthetic, it would be consistent" with Pistorius's story, Vermeulen said.

Roux also said a box of watches in Pistorius's home had gone missing, and he asked Vermeulen about any police inventory of items from the home. Vermeulen said he would not make an inventory of every item in a home where a crime has occurred.

Earlier, Roux pointed out that wood fragments went missing from the door after police investigators took possession of it. Vermeulen said he had searched for the fragments without success. Then the defence submitted a photo Wednesday which showed the missing fragments just a few feet away from Vermeulen.

Roux alleges investigator was biased

The lawyer also noted that Vermeulen had not read Pistorius's version of events on the night of the killing until after he had completed his forensic study of the door, and was therefore leaning toward the prosecution's version of what happened.

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A policeman was asked to demonstrate the effect of hitting a bathroom door with a cricket bat during the Pistorius trial on March 12. The prosecution and defence presented conflicting views about whether or not Pistorius was using his prosthetic legs when he broke down a bathroom door to get to his injured girlfriend. (Alexander Joe/Reuters)

Vermeulen said he had later briefly browsed through Pistorius's statement claiming the shooting was an accident when the forensic analyst had "nothing to do."

The colonel's testimony has also focused on a cricket bat that Pistorius said he used to break through the toilet door to get to Steenkamp after, according to his account, realizing his mistake.

On Wednesday, Vermeulen knelt and swung the bat to show how he believed Pistorius struck the door from a low angle, indicating he was on his stumps at the time. Roux insisted Pistorius was wearing his prosthetic legs, saying the bat marks on the door were low because he swung with a bent back.

The back-and-forth over whether Pistorius, the first amputee to run at the Olympics, was on his prosthetic limbs has gone on for two days at trial. It's important because it could either match Pistorius's account of the event, or point out inconsistencies.