Defense lawyer Barry Roux read excerpts from a psychologist's report that said the double-amputee runner is suffering from depression and post-traumatic stress disorder and "his condition is likely to worsen" if professional treatment for those conditions is halted.
The report by Dr. Jonathan Scholtz was compiled during a 30-day observation period at a state psychiatric hospital. A report was also compiled by three psychiatrists.
The experts concluded that Pistorius was not mentally ill when he fatally shot Steenkamp through a closed toilet door in the early hours of Feb. 14, 2013. The runner says he killed her accidentally, thinking he was about to be attacked by an intruder hiding in the toilet; the prosecution alleges he killed Steenkamp intentionally after a Valentine's Day argument.
Scholtz's report found that Pistorius did not have a history of "abnormal aggression or explosive violence" and found no evidence that he displays the narcissism associated with men in abusive relationships and linked to "rage-type" murders.
The prosecution has described the athlete as reckless and egotistical, given to jealousy, gun play and driving at high speeds..
Scholtz's report concluded he has a record of feeling insecure and vulnerable, particularly when he is without his prosthetic limbs, Roux said. That conclusion appeared to remove the possibility that Pistorius could be declared not guilty by reason of mental illness.
Also Wednesday, a medical expert who has treated Pistorius said the athlete has a hand tremor as well as a sleep disorder that required medication. Wayne Derman, a professor of sport and exercise medicine at the University of Cape Town, testified that he found Pistorius to be "hyper-vigilant" and was restless, often looking around quickly and scanning for possible threats.
"He is an anxious individual," Derman said.
He testified for the defense, which is trying to bolster the idea that the Paralympian's purported fear of crime may have pushed him to fire through a closed toilet door and that his disability contributed to an increased sense of vulnerability.
The court-ordered evaluation by the mental health experts occurred after a psychiatrist testifying for the defense said Pistorius was suffering from an anxiety disorder that may have influenced his actions on the night he killed Steenkamp.
At times during his trial, Pistorius has wailed and retched in apparent distress, particularly during graphic testimony about the shooting and also when the athlete was on the witness stand. At other times, he has been calm and taken notes. Chief prosecutor Gerrie Nel has suggested Pistorius feigned distress in order to dodge a tough cross-examination; the athlete's camp has denied his emotional displays were fake.
Pistorius, who is free on bail, faces 25 years to life in prison if found guilty of premeditated murder, but he could also be sentenced to significant time behind bars if convicted of murder without premeditation or negligent killing. He also faces gun-related charges.