Oscar Pistorius has pleaded not guilty to the murder of girlfriend Reeva Steenkamp as his trial began in Pretoria, South Africa.
The 27-year-old double amputee was asked by judge Thokozile Masipa if he understood the charge of murdering Ms Steenkamp, to which he replied: "I do, I do, my lady."
Asked how he pleaded, he said: "Not guilty, my lady."
Media swarmed the steps of North Gauteng High Court for the trial of Pistorius who shot Steenkamp dead at his home but claims he thought she was an intruder. The prosecution will argue it was pre-meditated murder.
The trial is expected to hear from more than 100 witnesses, including neighbours who claim to have heard screams from his house that night, as well as ex-girlfriends of the athlete.
Pistorius, wearing a dark suit, white shirt and dark tie, was ambushed by cameras as he made his way through the building to the courtroom.
Much of the trial will be broadcast live, and the case has already attracted global attention, with TV channels offering wall-to-wall coverage, including one 24-hour channel set up in South Africa exclusively for the trial.
Pistorius is accused of the premeditated murder of Steenkamp, who died of multiple gunshot wounds.
Prosecutors allege the paralympian shot the model and reality TV star four times through the locked bathroom door at his home in Pretoria in the early hours of February 14, 2013.
Some witnesses have described hearing a woman scream, followed by "moments of silence", then hearing gunshots followed by more screaming.
Pistorius claims he thought an intruder was in his home, but prosecutors say that even so, an "error in persona'' did not affect the fact he intended to kill someone.
Some 107 witnesses are listed by the state, including Steenkamp's close friends Desiree, Gina and Kim Myers, as well as Pistorius's sister Aimee and his uncle Arnold.
Steenkamp's family last month said her mother June will attend the trial as they said they were looking for "closure".
On the anniversary of Steenkamp's death, Pistorius made a statement on his website saying: "No words can adequately capture my feelings about the devastating accident that has caused such heartache for everyone who truly loved - and continues to love Reeva.
"The pain and sadness - especially for Reeva's parents, family and friends consumes me with sorrow.
"The loss of Reeva and the complete trauma of that day, I will carry with me for the rest of my life."
The mandatory sentence for someone convicted of premeditated murder in South Africa is life with a minimum of 25 years in prison, meaning if Pistorius is found guilty, he will be over 50 when he leaves prison.