PRETORIA, South Africa -- It was a corruption trial that had transfixed South Africa, and the prosecutor was in no mood for mercy. The defendant was the nation's top police official, a figure of such international stature that he had once led Interpol. But when he took the stand, his testimony -- his wife, he said, had accidentally shredded evidence -- was rejected outright by his inquisitor.
"You know what this means?" the prosecutor said. "That you are arrogant and that you lie."
When the trial ended, in 2010, the police commissioner, Jackie Selebi, was sentenced to 15 years, and the prosecutor, Gerrie Nel, had cemented a reputation for abrasive, in-your-face cross-examination that earned him a new nickname: the Pit Bull.
Now, Mr. Nel is focusing the same judicial laser on Oscar Pistorius, the celebrated amputee sprinter charged with the murder of Reeva Steenkamp, his girlfriend, in a trial that has fixated a much broader audience around the world.
Today, Mr. Pistorius is scheduled to return to the stand, beginning the second week of his testimony and the fourth day of painstaking cross-examination by Mr. Nel that has propelled the prosecutor into a global limelight rivaling the athlete's own renown as a fallen hero of the track.
Most graphically, Mr. Nel on Wednesday produced a photograph of Ms. Steenkamp's head wounds, with her brains exposed, and demanded that Mr. Pistorius look at it.
Judge Thokozile Masipa, warned him openly last week to stop calling Mr. Pistorius a liar while he was testifying. And the South African Human Rights Commission said Friday that it had received a complaint that Mr. Nel's persistent depiction of Mr. Pistorius as a liar infringed on the runner's right to be presumed innocent and to have a fair trial.
On Friday, Mr. Nel surprised observers by seeming to ease the pressure on Mr. Pistorius at a crucial moment when, for 31 seconds, the athlete was unable to say whether Ms. Steenkamp screamed as he fired the first of four shots on Feb. 14, 2013.
For all of Mr. Nel's renown in South Africa, his private life has been kept under wraps.