Chief prosecutor Gerrie Nel has talked to Prof. James Grant, a criminal law specialist at Johannesburg's University of the Witwatersrand, prosecution spokesman Nathi Mncube confirmed to The Associated Press.
"We are busy. We are considering appealing," Mncube said.
Pistorius started serving a five-year prison sentence on Tuesday after he was acquitted of murder by a judge and found guilty of a lesser charge of culpable homicide, or manslaughter, for shooting Reeva Steenkamp through a toilet door. The Olympic runner is eligible for release after 10 months and would then complete his sentence under house arrest.
Prosecutors insisted he should have been found guilty of murder and when Judge Thokozile Masipa acquitted the double-amputee athlete on that charge, her decision was widely questioned by legal analysts.
Grant, a television analyst during Pistorius' trial, was one of those. He wrote on Twitter earlier Friday that he had advised prosecutor Nel to appeal during their talks and agreed to assist if prosecutors decide to.
Experts say there are grounds for an appeal, partly because the judge may have misapplied a part of South African law called "dolus eventualis" — which says someone should be found guilty of murder if they foresaw the possibility of killing someone and went ahead anyway. The experts questioned how Masipa ruled that Pistorius did not predict that someone might die when he decided to shoot four times from close range into a small toilet cubicle in his home, hitting Steenkamp in the hip, arm and head.
Grant wrote online analyses of the case, arguing in one that "there appears to be nothing to save us from the inevitable conclusion that Masipa made errors of law and errors of logic."
Prosecutors have 14 days from the announcement of Pistorius' sentence on Tuesday to apply initially to Masipa for permission to appeal. They could appeal the verdict or Pistorius' sentence.
Mncube declined to comment on what they are considering appealing, but it's likely to be Masipa's decision to acquit the world-famous runner of murder.
Gerald Imray is on Twitter at www.twitter.com/GeraldImrayAPSuggest a correction