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(CNN) -- Video of Oscar Pistorius re-enacting how he says he killed his girlfriend was illegally obtained by the Australian television network that aired it Sunday, a lawyer for the former Olympian said.
The network says that isn't so.
Channel Seven's "Sunday Night" included the video in an hourlong report on the case against Pistorius, who is on trial for murder in the February 2013 shooting death of Reeva Steenkamp.
Pistorius, 27, admits firing the bullets that killed Steenkamp, but he says he mistakenly thought he was defending himself from an intruder. Prosecutors contend the two had an argument and he deliberately murdered the model and law school graduate, who was 29.
The video shows the disabled athlete walking on the stumps of his legs -- without his prosthetics -- while pretending to aim a handgun. Pistorius is also seen with his prosthetic legs carrying his sister down a set of stairs, which is intended to demonstrate how he says he carried Steenkamp.
The trial resumed on Monday as scheduled with no comment in court about the video.
The video was produced in October by a U.S. company hired by his defense team to help "visually map the events on the night of the accident" in preparation for the trial, Pistorius lawyer Brian Webber said in a statement to CNN.
The Evidence Room used the video to produce a "forensic animation" of the fatal events, Webber said. The defense never introduced it into the ongoing trial.
"We wish to make it very clear that the material that has been aired was obtained illegally and in breach of the nondisclosure agreement with The Evidence Room," Webber said. "Its usage also constitutes a breach of privilege as this material was produced for trial purposes on the instructions of a commissioner, and the ownership of the copyright vests in the commissioner. No permission for the disclosure thereof has been given."
CNN reached out to representatives of The Evidence Room for comment Sunday, but there was no immediate response.
The broadcast included an interview with Scott Roder, the investigator who produced the video.
Webber accuses the broadcaster of illegally purchasing the video and also violating a promise not to air it until after the trial is concluded.
The broadcast of the material is "a staggering breach of trust and an invasion of the family's privacy," the lawyer said.
"Whilst we cannot imagine how any of the footage would not support Oscar's version, we will only be in a position to comment further once we have had the opportunity to study what has been aired," he said.
Mark Llewellyn, the executive producer for "Sunday Night" issued a statement defending the use of the video.
"We would not have run the footage if we thought we had obtained it illegally," he said.
"The material shown on Sunday Night goes to the heart of both the prosecution and defense cases, including the account provided by Oscar Pistorius."
The video included Pistorius putting on his prosthetics to show how quickly he could do so after firing the gun.
He is also shown rushing across the floor on his stumps when prompted to demonstrate who fast he could move without his prosthetic legs.
At the trial's conclusion, Judge Thokozile Masipa will have to decide whether Pistorius genuinely made a mistake or deliberately murdered his girlfriend.
If Masipa does not believe the athlete thought there was an intruder, she will find him guilty of murder and sentence him to a prison term ranging from 15 years to life. South Africa does not have the death penalty.
If Masipa accepts that Pistorius did not know that Steenkamp was the person he was shooting at, she could find him guilty of culpable homicide, a lesser charge than murder, or acquit him, according to CNN legal analyst Kelly Phelps.
A verdict of culpable homicide would leave the sentence at Masipa's discretion.
The trial is is in its 38th day.
Testimony could end as early as Monday after the prosecution cross-examines Wayne Derman, a sports medicine doctor who has spent six years working with Pistorius. It's believed Derman is the final defense witness.
CNN's Robyn Curnow, Edwin Mesa and Carma Hassan contributed to this report.
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