Pretoria, South Africa (CNN) -- "Blade Runner" Oscar Pistorius broke down and vomited in court Monday as he heard a pathologist testify about his girlfriend Reeva Steenkamp's injuries after he shot her dead on Valentine's Day last year.
The testimony of pathologist Gert Saayman was interrupted by Pistorius' sobbing and retching, leading to a pause in the proceedings.
Earlier, Judge Thokozile Masipa imposed a broadcast blackout on Saayman's testimony. Masipa, who has been presiding over the weeklong trial in Pretoria, extended the ban to live reporting on Twitter.
Pistorius admits he shot Steenkamp, 29, but says that it was a tragic case of mistaken identity and that he thought she was an intruder who had broken into his home.
In court, Saayman confirmed that Steenkamp died from multiple gunshot wounds, consistent with having been hit in the head, arm and hip by three shots fired through the locked door of a toilet cubicle.
Pistorius appeared deeply physically distressed throughout the testimony, repeatedly making retching sounds and clutching his head in his hands. The track star, 27, appeared at times to try to cover his ears by clasping his hands behind his neck, or he put his fingers in his ears. His brother and sister came to check on him during the brief break in Saayman's testimony.
Security guard on the stand
Saayman said any of the three injuries to Steenkamp could have been fatal and all immediately incapacitating. He said it was probably the bullet to the skull that killed her almost immediately. It passed from the top of her head over her right eye to the base of her skull, suggesting that she was not standing when hit, he added.
Saayman said the wounds were consistent with "ranger" bullets, which open up "like the petals of a flower" to cause maximum tissue damage.
Earlier on Monday, defense lawyers challenged a security guard's statements about what happened on the night. Guard Pieter Baba said he talked by phone to Pistorius the night of the killing and Pistorius said "everything's fine" or "everything's OK."
But defense lawyer Barry Roux said Pistorius had said, "I'm fine."
Baba was adamant, saying, "What I just told the court is the truth."
Baba's testimony proceeded slowly because all questions and answers had to go through a translator. He gave two statements to police, months apart.
On Friday, Baba said he could hear Pistorius was crying and he knew everything was not fine.
Baba arrived at the house in time to witness Pistorius coming down the stairs carrying Steenkamp.
"I was so shocked, I couldn't think for a few moments," he testified.
Pistorius has pleaded not guilty to one charge of murder and a firearms charge associated with Steenkamp's killing as well as two gun indictments unrelated to her death.
Gun at his bedside
Another witness who testified Friday, former Pistorius girlfriend Samantha Taylor, said their relationship ended when he cheated on her with Steenkamp.
Prosecutor Gerrie Nel asked Taylor if she was ever at Pistorius' house when he thought there was an intruder. Taylor said yes.
She said Pistorius once heard something hit a bathroom window and woke her up to ask if she'd heard it, too, before taking his gun and going to investigate. Taylor said Pistorius woke her up other times when he thought he'd heard a noise.
Taylor also testified that Pistorius slept with a pistol on his bedside table or on the floor beside his prosthetic legs and once became so angry after a traffic stop that he shot a gun through the sunroof of a car.
Taylor said she met Pistorius in 2010, when she was 17, and they started dating the following year. She said they broke up twice, the second time on November 4, 2012, after he took Steenkamp to a sports banquet.
Roux asked if Taylor admitted in two e-mails to cheating on Pistorius. Taylor says she's never admitted to cheating on him but admits she had a relationship with another man after they broke up the first time.
Roux asked Taylor for details about the time he supposedly shot the gun out of the sunroof, but Taylor could not remember the name of the highway or the location in South Africa. She testified that Pistorius was angry and irritated after the traffic stop, even though he was not driving. She said he joked around about firing a shot and then laughed after he fired.
Nel put four neighbors of Pistorius on the stand in the first week of the trial, all of whom described hearing screaming and loud bangs they thought were gunshots the night of the killing.
Roux then tried to find inconsistencies or uncertainty in their stories. The defense goal is to prove there is a reasonable doubt about the guilt of the accused.
One of the most dramatic witnesses was a neighbor, Johan Stipp, who rushed to the track star's home the night he shot Steenkamp.
Pistorius broke down in court as Stipp said he saw Steenkamp lying on the floor, her brain tissue mixed with blood and Pistorius praying for her to live.
"I remember the first thing he said when I got there was, 'I shot her, I thought she was a burglar and I shot her,' " Stipp told the court in Pretoria.
Although Stipp is a prosecution witness, his testimony may bolster the defense case, CNN legal analyst Kelly Phelps said after Thursday's gripping testimony.
Prosecutors appear to have been trying to demonstrate that Pistorius and Steenkamp had a loud argument before the shooting, suggesting it's the reason he killed her.
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.
Pistorius and at least two neighbors made phone calls to security after the shooting, allowing the defense to use phone records to establish a timeline of events.
Stipp's version of events appears to coincide with the defense case, said Phelps, who teaches law at the University of Cape Town.
Trial may last three weeks
Judge Masipa will decide whether Pistorius is innocent or guilty. 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 gun indictment and 15 years for the firearms charge.
If he isn't convicted of premeditated murder, the sprinter could face a lesser charge of culpable homicide, a crime based on negligence, and could be looking at up to 15 years on that charge, experts said. The trial is expected to take at least three weeks.
Pistorius and Steenkamp were a young, attractive, high-profile couple popular in South Africa's social circles.
Pistorius, whose "Blade Runner" nickname reflects the special prostheses he uses while running, won six Paralympic gold medals and became the first double-amputee runner to compete in the Olympics, in London in 2012.
Steenkamp, a model who was soon to star in a TV reality show, was on the cusp of becoming a celebrity in her own right at the time of her death.
CNN's Richard Allen Greene reported from Pretoria and Ralph Ellis wrote from Atlanta. CNN's Emily Smith also contributed to this report.