The Paralympic gold medallist admitted killing law graduate and model Reeva Steenkamp, 29, in February 2013 by firing four shots into the locked door of a toilet cubicle. He said he thought an intruder was hiding in the cubicle.
Pistorius was convicted of culpable homicide, equivalent to manslaughter, last September and sentenced to five years in prison. During sentencing, Judge Thokozile Masipa said the state had failed to prove Pistorius intended to kill when he fired.
Prosecutors want the verdict changed to murder because, they argue, firing through the door when he knew someone was behind it meant Pistorius intended to kill, regardless of who was in the cubicle.
The state will argue that Masipa misinterpreted parts of the law and ignored important evidence. A murder conviction would result in a minimum sentence of 15 years in prison.
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A panel of five judges will hear the appeal. The judges could either reject the prosecution's appeal, order a retrial or convict Pistorius of murder themselves, legal experts say.
Pistorius was due to be released into house arrest in August after serving 10 months of his sentence. South African Justice Minister Michael Masutha blocked his release, saying procedure had not been followed.
Masutha referred the case to a parole review board, which is expected to hold a hearing next month.
(Reporting by Joe Brock, editing by Larry King)
