The girlfriend of Oscar Pistorius was shot in quick succession as she fell down, a forensics expert has told the South African athlete’s murder trial.
This differs from a police ballistics witness who said there was short break between the first and second shots.
Mr Pistorius denies intentionally killing Ms Steenkamp in early hours of Valentine’s Day last year.
He says he fired rapidly in fear through the toilet door after he mistook Ms Steenkamp for an intruder.
The prosecution says the 29-year-old model and law graduate was deliberately killed after the couple had an argument.
The double amputee Olympic and Paralympic athlete faces 25 years to life in prison if convicted of premeditated murder.
Forensics expert Roger Dixon, a defence witness, says Ms Steenkamp was standing at an angle to the door and that all four bullets hit her as fell to the ground.
Earlier in the trial, ballistics expert Captain Christiaan Mangena said he believed Ms Steenkamp was standing up facing the closed door when she was hit in the right hip.
He said she then fell back onto a magazine rack next to the toilet before three more bullets were fired at the door, one of which missed her.
The BBC’s Pumza Fihlani in court says Mr Dixon’s testimony challenges the state’s version that Ms Steenkamp would have had time to scream after the first bullet and that Mr Pistorius then changed aim and continued firing.
On Tuesday, Mr Dixon told the court his tests showed that with the light out, Mr Pistorius’ bedroom would have been almost completely dark on the evening of the shooting, despite a couple of LED lights.
This also supports Mr Pistorius’ evidence that he did not see whether Ms Steenkamp was still in bed when he got up.
The court also heard sound recordings Mr Dixon had made – of a cricket bat striking a door similar to the one in Mr Pistorius’ toilet, and of gunshots fired through the door at a distance of 60m (196ft) and 180m.
Mr Dixon seemed to struggle to tell the sounds apart, which the defence will use to cast doubt on what neighbours say they heard that night, our correspondent says.
Prosecution witnesses have testified to hearing a woman scream followed by gun shots, but the defence disputes their testimony, saying the only scream came from Mr Pistorius – after he had fired.
But prosecutor Gerrie Nel has sought to cast doubt on Mr Dixon’s credibility and qualifications as a forensics witness during his cross examination on Wednesday.
Mr Dixon is a geologist and university lecturer who worked as head of materials analysis at a police forensic laboratory in Pretoria for 18 years until 2012.
At the start of proceedings on Wednesday, the judge agreed to an application to postpone the case after Thursday’s hearings until 5 May.
Mr Dixon took the stand after seven days of testimony from the sprinter came to an end with him reading a Valentine’s Day card from his girlfriend.
If Mr Pistorius is acquitted of murder, the court must consider an alternative charge of culpable homicide, for which he could receive about 15 years in prison.
He also faces charges of illegally firing a gun in public and of illegally possessing ammunition, both of which he denies.
There are no juries at trials in South Africa, and his fate will be decided by the judge, assisted by two assessors.
Mr Pistorius is known as the “Blade Runner” because of the carbon-fibre prosthetics he uses on the track.
Mr Pistorius said in his statement at the start of the trial that he woke in the early hours and walked on his stumps to the balcony, pulled in two fans, closed the sliding door and drew curtains. He said that shortly before he had spoken to Reeva, who was in bed beside him.
He said he rejected prosecution claims that a witness heard arguing coming from the house before the shooting.
2. Bathroom window
Mr Pistorius said he heard the bathroom window sliding open and believed that an intruder, or intruders, had entered the bathroom through a window which was not fitted with burglar bars.
“Unbeknown to me, Reeva must have gone to the toilet in the bathroom at the time I brought in the fans,” he said.
Mr Pistorius said he approached the bathroom armed with his firearm, to defend himself and his girlfriend, believing Ms Steenkamp was still in bed.
Both sides agree four bullets were fired. Ms Steenkamp was hit three times.
Mr Pistorius said he fired his weapon after hearing a noise in the toilet which he thought was the intruder coming out of the toilet to attack him and Ms Steenkamp.
He said he was in a fearful state, knowing he was on his stumps and unable to run away or properly defend himself.
Mr Pistorius said he rejected claims that he was on his prostheses when he shot at the door.
A witness told the trial she woke to hear a woman screaming and a man shouting for help. She said that after the screams she heard four shots.
Mr Pistorius said he went back to the bedroom after shooting at the toilet door, still shouting for Reeva. Lifting himself up onto the bed, he felt over to the right hand side of it and noticed Ms Steenkamp was not there.
Mr Pistorius said this was when he realised she could have been in the toilet.
5. Toilet door
Mr Pistorius said he went back to the bathroom but the toilet was locked, so he returned to the bedroom, pulled on his prosthetic legs, turned on the lights before bashing in the toilet door with a cricket bat.
Forensics expert Johannes Vermeulen told the court that the height of the marks on the door caused by the cricket bat suggest Mr Pistorius was on his stumps at the time.
6. Emergency calls
Mr Pistorius’s defence team say he then called security at the gated housing complex and a private paramedic service before carrying Ms Steenkamp downstairs.
A security guard claimed it was the other way round, and he had called Mr Pistorius first after reports of gunfire. However, phone records shown to the court revealed Mr Pistorius called the estate manager at 3:19am, a minute later he called the ambulance service and at 3:21am he called estate security.
A minute later he received an incoming call – estate security calling him back.
According to police phone expert Francois Moller, Mr Pistorius called his friend Justin Divaris a short time later and just after 4:00am he called his brother Carl.