Olympic runner Oscar Pistorius has gone on trial in South Africa on charges he murdered his girlfriend at his home last year.
Pistorius was in court Monday in Pretoria, and told the judge he was not guilty of murder, recklessly discharging a firearm or illegally possessing ammunition.
"Do you understand the charges, Mr. Pistorius?"
"I do, I do, m'lady."
"How do you plead?"
"Not guilty, m'lady."
His defense team read a statement from Pistorius in which he admits to shooting model Reeva Steenkamp, but said that he mistakenly believed he was firing at an intruder who had broken into his bathroom.
Pistorius says he believed Steenkamp was still in bed, and that after hearing noise in the bathroom he believed the two of them were in imminent danger.
Prosecutors say Pistorius killed Steenkamp after an argument that night. They called their first witness, a neighbor, who told the court she heard "terrible screams" coming from Pistorius' home. She said there was a second set of screams, and then a series of gunshots.
If convicted of premeditated murder, Pistorius faces a life sentence.
Families of Pistorius and Steenkamp were also in court Monday, seated a few meters apart on opposite ends of a long bench.
The much-anticipated case has generated enormous media attention in South Africa and elsewhere. Parts of the trial are being broadcast live, and a South African station has launched a 24-hour channel dedicated to the proceedings.
The 27-year-old Pistorius is known as the "Blade Runner" for his carbon-fiber prosthetic legs. He competed in the 2012 London Olympics.