CAPE TOWN, South Africa >> Oscar Pistorius was eligible for parole in March under South African law and the double-amputee Olympic and Paralympic runner may have been wrongly denied early release from prison because of a miscalculation over when he began serving his sentence for murder, court documents show.

Justice and correctional services authorities submitted the documents to the country’s apex Constitutional Court on Tuesday and said they won’t oppose the appeal from Pistorius arguing he has served the prescribed amount of time in prison and should immediately be declared eligible for parole.

Offenders sentenced to more than two years in prison in South Africa must serve half their sentence to be eligible for parole.

Pistorius’ appeal says he was eligible when he attended a parole hearing on March 31, when a parole board denied his early release and ruled he was not eligible until August next year.

The new papers submitted to the Constitutional Court indicate that was an error and that authorities accept Pistorius had served half his sentence on March 21. They were submitted by a senior parole board official on behalf of South Africa’s minister of justice, the commissioner of the corrections department, and parole and prison authorities.

The confusion dates to Pistorius’ long and complex trial for the fatal shooting of girlfriend Reeva Steenkamp at his home in the predawn hours of Valentine’s Day 2013. The highly dramatic case went through numerous appeals in different courts, first over Pistorius’ conviction and then over his prison sentence.

The multiple Paralympic champion was ultimately convicted of murder and sentenced to 13 years and five months in prison in 2017 for shooting the 29-year-old model multiple times through a toilet cubicle door with his licensed 9 mm pistol. But that sentence only came after prosecutors successfully appealed a conviction on a lesser charge of culpable homicide — a charge comparable to manslaughter — and also an initial murder sentence of six years.

When South Africa’s Supreme Court of Appeal finally sentenced Pistorius to the 13 years and five months, there was a reason for that number. He should have been sentenced to 15 years, the minimum for murder in South Africa, but had already served a year and seven months between the time he was convicted of manslaughter and sentenced in late 2014 and the time it was upgraded to a murder conviction in July 2016.

The Supreme Court of Appeal counted that time and subtracted it from a 15-year sentence.

But, crucially, it should have started Pistorius’ new sentence from July 2016. In an apparent oversight, it ruled the new murder sentence should start on Nov. 24, 2017, the date it delivered its final judgment. That meant the 16 months between those two dates — when Pistorius was still in jail and his sentence was being appealed — was not counted.

Pistorius’ parole lawyer said in April that it was an “obvious mistake.” The new court papers also say that the Supreme Court of Appeal had “noted that it unfortunately” neglected to include that extra time Pistorius served.

But while the court error appears to be clear, the Supreme Court of Appeal has not yet delivered a judgment correcting its mistake.

So, when parole board officials asked the Supreme Court for clarity over Pistorius’ sentence ahead of his parole hearing in March, a clerk from the Supreme Court replied that there was no new judgment changing the dates, justice authorities said in their papers to explain what happened with Pistorius’ parole hearing. The parole board then had no option but to rule Pistorius ineligible, they said.

Pistorius is appealing to the Constitutional Court, the highest in South Africa. He is asking to be declared eligible to be considered for parole immediately. The Constitutional Court has yet to hear the appeal and the court documents were submitted as pre-hearing papers.

Even if Pistorius does get a new parole hearing, it’s not certain he will be released from the Atteridgeville Correctional Centre in the capital, Pretoria, where he has served seven of his nearly nine years in prison.

Parole boards take a wide range of factors into account when considering if an offender can be released early and placed under correctional supervision at home, including submissions from the victim’s relatives.

Steenkamp’s parents, Barry and June, opposed Pistorius’ parole in March. Barry Steenkamp died last week at the age of 80. He had said earlier this year that Pistorius should remain in prison.