Oscar Pistorius faces a return to prison after South Africa's Supreme Court of Appeal ruled his initial manslaughter conviction for killing girlfriend Reeva Steenkamp should be changed to murder.
Pistorius was handed a five-year jail term last October for the "culpable homicide" of Steenkamp, whom he killed by firing shots through a locked bathroom door on Valentine's Day 2013.
The Paralympic gold medallist, who said he thought Steenkamp was an intruder, was released and put under house arrest this October, having served a fifth of his sentence.
However, prosecutors said Pistorius should have been charged with murder - arguing the application of the law in his trial was not correct - and the Supreme Court of Appeal ruled in their favour on Thursday.
"People must be convicted of the crimes they have committed and not of lesser offences," Justice Eric Leach said.
"[A retrial would be] wholly impractical and not in the public interest.
"I have no doubt the accused must have foreseen, and therefore did foresee, that whoever was behind the door might die, but reconciled himself to that even occurring and gambled with that person's life. The identity of his victim irrelevant to his guilt.
"His evidence is so contradictory that one does not know his true motivations," Leach added, claiming Pistorius fired the fatal shots without "rational thought".
"In the result of count one in the indictment the accused ought to have been found guilty of murder, on [the] basis that he had fired the shots with criminal intent.
"As a result of the errors of law referred to and a proper appraisal of the facts, he ought to have been convicted not of culpable homicide on that count, but of murder.
"In the interest of justice the conviction and the sentence imposed must be set aside and the conviction substituted with a conviction of the correct offence.
"The matter is referred back to the trial court to consider an appropriate sentence afresh in the light of the comments in this judgment."
No mention was made with regards to Pistorius' current status, with the South African currently out of prison under house arrest, nor has a date has been set for the reconvening of the high court in Pretoria for a fresh sentencing on the murder conviction.