The case for his conviction hinges on the fact that Oscar, who is a famous Paralympian, got out of bed to put on his prosthetic legs before shooting through the bathroom door, killing his girlfriend Reeva Steenkamp.
The prosecution allege this proves the murder was premeditated, discrediting his claim that he was panicked by the thought of an intruder in the house.
And now prosecutors have admitted they are not sure if the athlete was wearing his prostheses or not.
In fact, ballistic experts say the 27-year-old was 'most likely' on his stumps when he shot through the door repeatedly, removing the element of pre-meditation.
The gold medal winning athlete, dubbed 'blade-runner' because of the fibre-optic blades he competes with, posted a tribute to Reeva on the anniversary of her death, Valentine's Day.
'The pain and sadness - especially for Reeva's parents, family and friends consumes me with sorrow.'
'The loss of Reeva and the complete trauma of that day, I will carry with me for the rest of my life.'
'The loss of Reeva and the complete trauma of that day, I will carry with me for the rest of my life.'
Pistorius had his legs amputated below the knee aged 11 months, because he was born without the fibula bone, and Doctor's felt he would have a greater chance of mobility with prosthetics.
His girlfriend, Reeva, who tragically died aged just 29, was a successful South African model and presenter. She was also studying to pass her bar exam, and worked as a paralegal around modelling commitments.