Oscar Pistorius has been cleared of murder in the killing of his girlfriend Reeva Steenkamp, but he could still end up behind bars.

The judge in his trial will begin a second day of reading her verdict Friday, with all the signs pointing toward a conviction for culpable homicide. That's the South African term for unintentionally -- but illegally -- killing a person.

Judge Thokozile Matilda Masipa, who has presided impassively for months over the high-profile trial, finally let the world know what she has been thinking as she began reading her verdict Thursday.

Most importantly, Pistorius did not intend to kill Steenkamp, Masipa said, accepting his defense that he thought someone had broken into his house and that he believed he was defending himself.

Pistorius, 27, has always admitted firing the bullets that killed his girlfriend Steenkamp, then a 29-year-old cover model about to turn reality TV star. He pleaded not guilty to murdering her in his home on Valentine's Day last year, claiming that the killing was a tragic mistake.

But in grabbing his gun and heading toward the supposed threat, Pistorius "acted too hastily and used excessive force," Masipa ruled Thursday.

"His conduct was negligent," and not what a reasonable man would do in the circumstances -- not even a disabled one, she said before adjourning for the day.

Defense arguments that his upbringing "in a crime-riddled environment and in a home where the mother was paranoid and always carried a firearm" might explain his conduct that night, but "it does not excuse the conduct," Masipa said.

"The accused had reasonable time to reflect, to think and to conduct himself reasonably," she said. "I am not persuaded that a reasonable person with the accused's disabilities in the same circumstances would have fired four shots into that small toilet cubicle."

Though she did not formally pronounce Pistorius guilty of culpable homicide, her statements from the bench essentially added up to a definition of the crime, said CNN legal analyst Kelly Phelps.

There is no minimum sentence for culpable homicide in South African law, so it will be up to the judge to decide his sentence if that is her verdict. Sentencing takes place in a separate phase of the trial that can come weeks after the verdict.

(CNN)