In this Oct. 17, 2014 file photo, Oscar Pistorius is escorted by police officers as he leaves the high court in Pretoria, South Africa.
Seen here with Reeva Steenkamp
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.
But the 28-year-old could soon be back in prison if prosecutors are successful in their argument in the appeal court filed Monday 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 of being released on house arrest while the court could over-turn the verdict and 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 the Valentine's Day in 2013.
But he said he mistook the 29-year-old for an intruder. Prosecutors insist that he deliberately killed the her after an argument.
They are appealing both the judgement and the sentence, calling the five-year jail term "shockingly light". Prosecutors argue in the appeal papers that even based on the athlete's own version of events, Pistorius "knew there was a person behind the closed door" and "deliberately fired shots into the door".
"The only conceivable finding... should be that he intended to kill the person in the cubicle," they say, adding that Pistorius' evidence "can never be found to be reasonably possible".
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.
"He's not out on parole on the 21st of August, he's having his sentence converted to a house arrest sentence," said David Dadic, a criminal lawyer based in Johannesburg.
"He's now confined to a house for a period until he's actually on parole," said Dadic. "They'll confine him essentially to what he would be doing in prison but in the confines of his own house."
He may have to wear an electronic tag and undergo some kind of community service.
While there is speculation that Pistorius will serve his house arrest at his wealthy Uncle Arnold's house -- a mansion in a posh Pretoria suburb -- there is a possibility the athlete will ask to serve his sentence in a different location, away from the glare of the media.
"I think he's going to come out very quietly, and very discreetly and he’s going to disappear and stay off the radar," said lawyer Martin Hood.I believe he does not want to stir up any more public censure, negativity or deal with anyone who feels justice was not served with such a light sentence.
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.
"We fear that this will not send out the proper message and serve as the deterrent it should."Many feel this trial was a farce and serves a testament to what fame, money and connections can buy a murderer.