Oscar Pistorius’ mental condition has worsened since his trial and he has “almost given up” on life, a psychiatrist has told a court.

Professor Jonathan Scholtz said the athlete now suffered more severe post-traumatic stress disorder, agoraphobia, depression and generalised anxiety disorder than when he stood trial two years ago for the murder of girlfriend Reeva Steenkamp.

As a result, his mental state is now “too severe” for him to give evidence in mitigation of his sentence which will be handed down in Pretoria’s High Court in the coming days.

Professor Scholtz, who was also the court-appointed psychiatrist who evaluated him as an inpatient at a nearby psychiatric hospital during his trial, said the athlete had become increasingly forgetful and was sleeping for extended periods.

As he listened to the testimony, the 29-year-old former paralympian wept and wiped his nose, his eyes puffy and reddened from frequent crying.

“I feel unfortunately his condition has worsened. He really has almost given up, his spirit seems broken,” he said.

He argued that there would be no point sending the Blade Runner, as he was once known for the carbon fibre prostheses he competed on around the world, back to prison.

He pointed to his youth, his lack of previous offending or risk of future crime-committing, his intelligence and his desire to help others as evidence that he would be more useful in the outside world.

He said his uncle Arnold, with whom he has been living since he was released on parole in October, had offered him a job with his company Twin City working in early child development.

“It is my considered opinion prison would have a detrimental affect on Pistorius as a person (to send him back to prison),” he told the court. “It would not be constructive. It would be better if he gave back in constructive ways – using his skills to enhance the lives of others.”

Professor Scholtz described a number of “unfortunate incidents” during Pistorius’ time in prison, including him hearing a young man raped who hung himself the next morning. He said the double amputee had been forced to sit on a concrete floor to shower for the first five weeks of his incarceration, leaving him with a severe infection.

He said Pistorius had at one point been confined in his cell for up to 18 hours a day, a punishment akin to “torture” for many people. He said at night he would often wake to find prison officials peering at him through the bars of his cell, leaving him feeling “like an animal in a cage”.