South African prosecutors on Monday filed an appeal calling for Paralympian star Oscar Pistorius to be convicted of murder for killing his girlfriend – just days before he is due to be released from prison. Pistorius has spent less than a year behind bars since being convicted in a sensational trial on the lesser charge of culpable homicide, and is expected to leave jail on Friday for a form of house arrest. I think the chances are pretty good that the appeals court will rule in favour of the state and overturn the verdict Criminal lawyer Ulrich Roux But the 28-year-old could soon be back in prison if prosecutors are successful in their argument in the appeal court that he should have been convicted of murder rather than culpable homicide – a charge equivalent to manslaughter. If they win their case, which is expected to be heard in November, Pistorius could face at least 15 years in jail. The athlete – known as the “Blade Runner” for the prosthetic legs he wears on the track – won international fame after racing against able-bodied competitors in the 2012 London Olympics, and his trial was broadcast live around the world. “I think the chances are pretty good that the appeals court will rule in favour of the state and overturn the verdict,” said Ulrich Roux, a criminal lawyer in Johannesburg. “He is faced with the unusual circumstance that he’s released on house arrest and then the court could find him guilty of murder and he’ll have to return to prison.” Pistorius does not dispute that he shot model and law graduate Reeva Steenkamp four times through a locked toilet door in his Pretoria home in the early hours of Valentine’s Day in 2013. But he said he mistook the 29-year-old for an intruder. Prosecutors insist that he deliberately killed her after an argument. They are appealing against both the judgment and the sentence, calling the five-year jail term “shockingly light”. The athlete’s defence team has until September 17 to file its response. South African correctional services officials have indicated that Pistorius has been a good inmate and qualifies for house arrest – a routine procedure in South Africa. Steenkamp’s family has expressed dismay at his imminent release. “Incarceration of 10 months for taking a life is simply not enough,” Steenkamp’s parents Barry and June said in a statement.