Oscar Pistorius
South African Olympic and Paralympic athlete Oscar Pistorius sits in the dock during his murder trial in the North Gauteng High Court in Pretoria June 30, 2014. Pistorius is on trial for murdering his girlfriend Reeva Steenkamp at his suburban Pretoria home on Valentine's Day last year. Reuters/Ihsaan Haffejee/Pool

Oscar Pistorius’ trial resumed Monday with experts claiming that the South African Olympian didn't suffer any mental illness when he shot and killed his 29-year-old girlfriend, Reeva Steenkamp, last year, media reports said, citing psychological reports.

The double-amputee’s mental health was evaluated after defense lawyers claimed that the athlete suffered from an anxiety disorder. Judge Thokozile Masipa said that it was necessary to understand if the 27-year-old’s mental condition affected his ability to distinguish between right and wrong. In the middle of the murder trial, Masipa ordered Pistorius to undergo a month-long assessment at Weskoppies Psychiatric Hospital in Pretoria, the South African capital.

"Mr. Pistorus did not suffer from a mental illness or any defect that would have rendered him criminally not responsible for the offence charged," state prosecutor Gerrie Nel said, reading from the psychologist report, according to the Huffington Post UK.

Pistorius and his defense team have argued that the sprinter mistook Steenkamp for an intruder when he shot and killed her on Valentine's Day 2013 at his home in Pretoria. Pistorius faces 25 years to life in prison if found guilty of premeditated murder, and could also face years in prison if convicted of murder without premeditation or negligent killing. He's free on bail.

Before sending Pistorius for an evaluation, Masipa said that psychiatrists would "inquire into whether the accused by reason of mental illness or mental defect was at the time of the commission of the offense criminally responsible for the offense as charged."

Defense psychiatrist Merryll Vorster testified earlier that Pistorius’ physical disability gave him an increased level of stress.

"There is no doubt that children who have bilateral amputations at the age of 11 months find that very stressful" Vorster previously said, claiming that it led to the development of generalized anxiety disorder in Pistorius.

The defense is expected to finish presenting evidence in the next few days followed by a verdict.