The Paralympian has spent the past month being assessed in a mental health facility as part of the trial, where he stands accused of murdering model Reeva Steenkamp.
A psychological report has revealed Oscar was not suffering from a mental disorder at the time of the shooting, and so should be held criminally responsible for his actions.
Pistorius has maintained throughout the trial that he shot his girlfriend by accident, after mistaking her for an intruder in his home.
READ: Pistorius sent for mental evaluation
However the prosecution allege the athlete shot his lover in cold blood after an argument.
The trial resumed after a 30 day adjournment this week, and this morning heard from Professor Derman, who said levels of anxiety and stress are higher among disabled athletes than their able-bodied counterparts.
READ: Defence claim Pistorius suffers from anxiety disorder, causing him to be hyper vigilant
The Psychologist said that Pistorius is indeed an anxious individual who is 'severely traumatised' following the death of Steenkamp in February 2013.
It is thought Professor Derman may be the last witness in the murder trial, which has been ongoing since March.