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PRETORIA, South Africa (CNN) -- Reeva Steenkamp, the girlfriend of Oscar Pistorius, was seated on a magazine rack in a defensive position when he fired through a door killing her, a police ballistics expert said Wednesday in the Olympian's murder trial.
Police Capt. Christian Mangena said the nature of Steenkamp's wounds indicates she was covering to protect herself.
He described Tuesday how he used lasers to track the path of the bullets that Pistorius fired through a door, coming to the conclusion that "the shooter was most likely not wearing prosthetic legs."
Mangena previously testified that he had Pistorius' height checked with and without his prosthetics.
The height of the four bullet holes in the door ranged from 93.5 centimeters (3 feet) to 104.3 centimeters (almost 3.5 feet) above the floor.
Without his prosthetic legs on, the double amputee runner's elbow height is 96 centimeters (just over 3 feet), Mangena said.
Mangena said Wednesday that he analyzed three possible shooting position and determined that firing without the prosthesis was most probable. Less likely was that Pistorius was on his prosthetic legs, but holding the gun lower. He deemed it impossible that Pistorius was lying on the ground, holding the gun above his head.
The runner maintains that he was not wearing his prosthetics when he killed Steenkamp, and after suggesting at his bail hearing last year that he was wearing them, the prosecution conceded last week that he was not.
The one-time South African national hero admits that he killed Steenkamp on February 14, 2013, but pleaded not guilty to murder, saying the killing was a terrible mistake.
He thought she was an intruder in his house in the middle of the night, and mistakenly believed he was defending himself, he maintains.
That he was not wearing his prosthetics is a vital part of his defense. He argues he was justified in shooting through a toilet room door because he is particularly vulnerable when he is on the stumps of his legs.
Photos of victim's wounds
On Tuesday, Pistorius listened to much of the testimony impassively, but covered his face with his hands and stuffed his fingers in his ears when Mangena talked about needing to see Steenkamp's dead body as part of his investigation.
"I have to see the position of all the injuries sustained," the 20-year police veteran said, before leafing through photos of bullet holes in the black sleeveless top she was wearing, her face and injuries to her body.
Pistorius spent hours throwing up in court last week as Steenkamp's injuries were described by the witness who did her autopsy, and later when pictures of her injuries were briefly accidentally flashed on courtroom monitors.
Steenkamp's mother June was in court Tuesday and appeared to be crying when photos of the bathroom where her daughter died were displayed.
A police crime scene photographer was on the witness stand for much of the day Tuesday as defense lawyer Barry Roux tried to show that police photos were not reliable evidence.
He got the photographer, Bennie van Staden, to say there was definitely no one else in the bathroom with him when he took pictures of the blood-spattered scene, then produced photographs which he said another police officer took in the same room at the same time.
"You did not see him in the bathroom?" Roux demanded.
"I did not see him," van Staden replied.
"And how big is this bathroom?" Roux asked incredulously, prompting laughter.
"Approximately 4 by 4 meters," van Staden replied with a shrug.
Prosecutor Gerrie Nel fought back when questioning the photographer later, producing a photograph taken by the officer whom Roux said was in the same room at the same time.
"Are you in this photograph?" Nel asked.
"No," van Staden replied, eliciting a fresh burst of guffaws.
Roux also introduced a statement from another police officer, blood spatter expert Ian van der Nest, to defend his client.
Van der Nest's affidavit said the blood he saw in the house was not only "consistent" with Pistorius' version of events, but was the "most probable explanation."
He is on the list of possible prosecution witnesses but has not testified yet.
Mangena is the 16th state witness, out of a potential 107.
The trial is currently scheduled to run through April 4, take a break, and resume in mid-April.
There's no question that Pistorius shot Steenkamp through a bathroom door in his house early on Valentine's Day last year, hitting her with three hollow-tipped bullets, one of which probably killed her almost instantly. Pistorius says he heard a noise in the middle of the night after getting out of bed, did not realize that she had also gotten out of bed, got his gun and shot her by accident.
Pistorius first achieved fame as an outstanding double amputee sprinter who runs with special prostheses that earned him the nickname "Blade
The case against Pistorius is largely circumstantial, Nel said in his opening statement on March 3. Pistorius and Steenkamp were the only people in his house when he killed her.
Nel has been building a picture of what happened through the testimony of police officers, experts, neighbors who heard screaming and bangs that night, current and former friends of Pistorius' and a security guard who sped to the scene because of reports of gunshots.
Neighbors said they heard a woman screaming before the shots were fired. But the defense is proposing that what neighbors thought was Steenkamp screaming in fear for her life was in fact Pistorius when he realized what he had done.
And the defense says that the sounds neighbors heard were not the gunshots, but a cricket bat hitting the door as he tried to rescue her.
Judge Thokozile Masipa will decide the verdict with the help of two lay people called assessors. South Africa does not have jury trials.
In South Africa, premeditated murder carries a mandatory life sentence with a minimum of 25 years. Pistorius also could get five years for each of two unrelated gun indictments and 15 years for a firearms charge he also faces.
If he isn't convicted of premeditated murder, the sprinter could face a lesser charge of culpable homicide, a crime based on negligence.
The sentence for culpable homicide is at the judge's discretion.
CNN's Robyn Curnow, Brent Swails, Nicola Goulding and Emily Smith contributed to this report.
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