Oscar Pistorius has been found guilty of murder after his previous conviction of manslaughter was overturned.
The Paralympian "ought to have been convicted, not of culpable homicide, but of murder", judge Leach said this morning. The original ruling was "confusing and flawed", he said.
Pistorius killed his girlfriend Reeva Steenkamp on Valentine's Day 2013, after shooting her through a locked door.
He received a five year sentence for culpable homicide - South Africa's equivalent of manslaughter - and has served less than a year before being transferred to his uncle's mansion, where he is under house arrest.
The athlete will have to return to court for a new sentence to be decided, but it is likely he will return to prison.
The principles of dolus eventualis - a legal term used to denote intent - were incorrectly applied, he added. Pistorius should have foreseen that shooting into a small area would result in death.
During last year's trial, judge Masipa ruled that the state had failed to prove intent - or dolus eventualis - meaning he was convicted under manslaughter.
The state sought an appeal on the conviction, claiming the judge misinterpreted the law of dolus eventualis.
Reports initially suggested the appeal had been dismissed, however Judge Leach was referring to another matter.
Watch Judge Leach hand down the verdict in the video below.