Oscar Pistorius arrived in court this week for the start of his sentencing phase of his trial in the shooting death of his girlfriend Reeva Steenkamp last year.

Pistorius, a famed Paralympic athlete nicknamed the "Blade Runner," fatally shot Steenkamp on Feb. 14, 2013. The pro-athlete pleaded not guilty to first degree murder, arguing that he shot her by mistake because he thought she was an intruder in his home. However, prosecutors in the high profile case claimed that he killed her out of rage after the couple had an argument in the wee hours of Valentine's Day.

Last month, Judge Thokozile Matilda Masipa ruled that Pistorius is guilty of culpable homicide, a lesser charge also known as manslaughter, which is punishable with up to 15 years in prison, reports Fox News.

On Monday, the athlete's psychologist described Pistorius as is a "broken man" who is devastated by the lost of his girlfriend during his testimony.

"We are left with a broken man who has lost everything. He's lost his relationship with Reeva Steenkamp, he's lost his moral and professional reputation. He's lost his friends. He's lost his career," said Dr. Lore Hartzenberg, according to ABC News. "On an emotional level, his self-perception and self-worth have been damaged."

Joel Maringa, a social worker and defense witness, also testified Monday, suggesting that the paralympian sprinter be sentenced to three years of house arrest and community service.

In response, Prosecutor Gerrie Nel said the suggestion of three years of "correctional supervision" was "shockingly inappropriate," reports ESPN.

Pistorius' sentencing phase is expected to last for most of the week. The sentence can range from a hefty fine to over a decade behind bars.

According to a legal expert speaking on the condition of anonymity, Judge Masipa will likely prepare a written judgment on sentencing since the high profile case involved complex legal issues, reports IOL News.