Dr. Jonathan Scholtz said Pistorius was suffering from “major depression” as he faces a 15-year jail term for the 2013 murder of his girlfriend Reeva Steenkamp and that a jail term would not be “constructive.”

“Since the offense, he has developed a serious psychiatric condition which has become worse over the past two years,” Scholtz told the court.

MORE: Where disgraced athletes went wrong

Meantime, state prosecutor Gerrie Nel challenged Scholtz’s assertion that Pistorius wasn’t fit to testify in the sentencing hearing, pointing out that Pistorius recently sat for an hour-long interview with British broadcaster ITV.

Pistorius’ potential sentence could be reduced to time served because of mitigating factors, the BBC reported.

He claimed he fired four shots through a bathroom door because he thought an intruder was in his house. Originally jailed on manslaughter charges, he was released into house arrest after a year. But South Africa’s Supreme Court changed his conviction to murder after the prosecution appealed.

MORE: Most heinous crimes connected to athletes

The sentencing hearing is expected to last all week with a sentence due by Friday.