South African prosecutors have said they will file appeal papers in the next few days against the verdict and sentencing in the case of Oscar Pistorius, who was given a five-year prison term after being convicted of culpable homicide for killing his girlfriend.
The National Prosecuting Authority's decision to appeal could see the Olympic runner face a murder charge again for shooting Reeva Steenkamp, and a minimum of 15 years in prison if he is found guilty on appeal.
Pistorius, the 27-year-old double-amputee athlete, was acquitted of murder by Judge Thokozile Masipa last month for shooting Ms Steenkamp multiple times through a toilet cubicle door in his home in Pretoria. He said he mistook her for a night-time intruder. Judge Masipa found him guilty instead on a charge comparable to manslaughter.
The NPA said in a statement its decision to appeal was based on a "question of law", meaning it believes that Judge Masipa misapplied the law when she acquitted Pistorius of murder.
"The merits and the demerits of the NPA's argument ... will become evident when we file papers for leave to appeal," the NPA, South Africa's national prosecuting body, said. "The prosecutors are now preparing the necessary papers in order to be able to file within the next few days."
Chief prosecutor Gerrie Nel and his assistant, Andrea Johnson, had been "hard at work studying the judgment, researching and also consulting with legal experts with the view to establish whether or not there are sufficient grounds to appeal both the judgment and sentence", the NPA said.
Prosecutors have to apply initially to Judge Masipa for permission to appeal within 14 days of Pistorius's October 21 sentencing.
Pistorius's lawyer, Brian Webber, declined to comment, while Pistorius's uncle, Arnold Pistorius, released a short family statement saying: "We take note of the state's announcement. The law must take its course."
Pistorius started serving his prison sentence last week for negligently killing Ms Steenkamp on February 14 2013. Under the current terms of his sentence, the multiple Paralympic champion is eligible for release after 10 months and would then complete his sentence under house arrest.
At the time of the sentencing, prosecutors said they were disappointed with the culpable homicide conviction and believed they had a strong murder case against Pistorius. A murder conviction in South Africa has a minimum of 15 years in prison.
Mr Nel laid the groundwork for the decision to appeal, speaking with Professor James Grant, a criminal law specialist at Johannesburg's University of the Witwatersrand, prosecution spokesman Nathi Mncube said.
Judge Masipa's decision to acquit Pistorius of murder had been questioned by legal analysts. Prof Grant, a television analyst during Pistorius's trial, was among them and said last week that he had advised Mr Nel to appeal. Prof Grant also said he agreed to assist prosecutors.
Experts say there are grounds for an appeal, partly because the judge may have misapplied a part of the law called "dolus eventualis" - which says someone should be found guilty of murder if they foresaw the possibility of killing someone through their actions and went ahead anyway.
The experts questioned how Judge Masipa ruled that Pistorius did not predict that someone might die when he decided to shoot four times from close range into the small toilet cubicle in his Pretoria home, hitting Ms Steenkamp in the hip, arm and head.
Some experts have also said that Pistorius's argument that he did not know it was his 29-year-old girlfriend in the cubicle might not be enough to save him from a murder conviction as he still knew there was someone in there when he fired his 9mm pistol.