Perhaps anticipating a challenge by prosecutors, Judge Masipa said in her ruling Wednesday morning that she would be available to receive a request for an appeal that same day.

Among other mitigating factors, the judge said she considered the circumstances of the shooting and Mr. Pistorius’s disability.

She also noted that Mr. Pistorius was a first-time offender who had shown himself to be a good candidate for rehabilitation. “I am of the view that a long-term imprisonment will not serve justice,” Judge Masipa said.

In remarks largely sympathetic to Mr. Pistorius, the judge added: “He’s a fallen hero who has lost his career and is ruined financially. The worst is that having taken the life of a fellow human being in the manner that he did, he cannot be at peace.”

Marius du Toit, a criminal defense lawyer, former prosecutor and judge who has closely followed the trial, said the sentence, though “erring on the side of leniency,” clearly reflected the judge’s belief that Mr. Pistorius was guilty of what amounts to an accidental murder, not one with intent.

Mr. du Toit said that prosecutors could decide to contest the sentence by asking Judge Masipa to grant leave to appeal or, failing that, by petitioning the Supreme Court of Appeals directly.

“But is it something that another court will interfere with? I somehow don’t think so,” he said. “I think we may have reached the end of this matter.”