JOHANNESBURG — (CNN) Prosecutors in South Africa, saying the trial judge misinterpreted the law, are seeking to have Oscar Pistorius convicted of murder for shooting his girlfriend, Reeva Steenkamp, to death on Valentine’s Day 2013.

Prosecutor Gerrie Nel told the five judges presiding over the hearing in Bloemfontein that the judge at the trial had made an error of law.

Pistorius, once an athletic golden boy, does not deny shooting Steenkamp to death through a bathroom door, but he has maintained that he thought there was an intruder there.

He was convicted in 2014 of culpable homicide — a lesser charge than murder — and sentenced to five years in prison.

He was released after less than a year, to serve the rest of his sentence under house arrest.

Tuesday’s hearing hinges on the principle of “dolus eventualis,” or intent — the legal principle that the perpetrator foresaw that his act could cause death and went ahead nevertheless.

High court Judge Thokozile Masipa ruled last year that the state had failed to prove that Pistorius intended to kill Steenkamp.

But prosecutors are arguing this was a misapplication of the principle of dolus eventualis, and that Pistorius knew that shooting through the door could cause the death of whoever was inside.

“On the objective facts, the accused can not escape the conviction of murder,” Nel told the judges Tuesday.

Should the prosecution succeed, Pistorius could be returned to prison.

Pistorius, a double amputee known for his prostheses as the “blade runner, competed with able-bodied runners in the 400 meters in the 2012 Summer Olympic Games in London.

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