SOMERSET WEST, South Africa — A judge “overemphasized” Oscar Pistorius’ disability and was far too lenient on the double-amputee athlete, prosecutors said Friday as they tried to convince a South African court to more than double his prison sentence from six to 15 years for the murder of girlfriend Reeva Steenkamp.

“Murder is murder,” chief prosecutor Andrea Johnson told a five-judge panel at the Supreme Court of Appeal. She asked them to overturn Pistorius’ initial sentence and give him the prescribed minimum of 15 years. There is no death penalty in South Africa.

If the court agrees with prosecutors that he deserves a harsher sentence, Pistorius, now 30, could remain in prison until after he turns 40.

The judges did not deliver a decision on Friday. Typically, Supreme Court judges take a couple of weeks before the senior judge returns to read out the decision, which is made through a simple majority.

Nearly five years after the once-admired Olympic runner first appeared in court for shooting Steenkamp multiple times through a closed toilet door at his home, Pistorius’ fate is still not certain.

He was not present at Friday’s hearing as he serves his sentence at a prison near the capital, Pretoria. He has served more than a year of his six-year term. Steenkamp’s mother, June Steenkamp, did attend. Speaking outside the courthouse, her lawyer said the Steenkamp family supported prosecutors’ attempt to get a longer sentence.

Prosecutors had two arguments to make to the court. First, they needed to apply for permission to appeal Pistorius’ sentence. They were asked by the judges to also present their arguments for why, if their appeal is allowed, his sentence should be increased.

This is the second time prosecutors have gone to the Supreme Court in the central city of Bloemfontein to challenge a decision by Judge Thokozile Masipa, who presided over Pistorius’ trial.

In 2015, prosecutors successfully appealed against Masipa’s judgment that Pistorius was not guilty of murder. The court overturned Masipa’s verdict of culpable homicide — or manslaughter — and convicted Pistorius of murder.

Legal analysts say, however, it is more difficult to get the court to change a sentence.

After the manslaughter conviction was overturned, Masipa sentenced Pistorius to six years in prison for murder, a term just one year longer than her original sentence for manslaughter. Prosecutors called that sentence “shockingly” light.

Judges can deviate from prescribed minimum sentences if there are compelling circumstances. The prosecution says there were no compelling reasons.

“What we are saying is the court exercised its discretion inappropriately,” prosecutor Johnson said, calling the six-year sentence “unjust.”

She said Pistorius still had not shown “genuine remorse” for killing Steenkamp and that Masipa put the athlete’s personal circumstances and his disability ahead of the need for “retribution” when she sentenced him.

Pistorius claimed he mistook Steenkamp for a dangerous intruder hiding in his bathroom in the pre-dawn hours of Valentine’s Day 2013 when, without his prosthetic legs on, standing on his stumps and feeling vulnerable, he shot four times through the cubicle door.

Masipa’s initial sentence was appropriate in the circumstances, Pistorius’ defense lawyers said, and his disability was not exaggerated. Pistorius had both his legs amputated below the knee when he was a baby because of a congenital condition.

“Of course his disability is mentioned, but it can’t not be mentioned,” defense lawyer Kelly Phelps said. “It is one of the factors of this case. We can’t magic away his disability.”