South African athlete Oscar Pistorius has returned to court for sentencing after being convicted of killing his girlfriend, Reeva Steenkamp.

Pistorius was found guilty of the culpable homicide of Ms Steenkamp last month but he was cleared of murder.

His psychologist was the first defence witness to speak at the sentencing hearing, which could last several days.

Pistorius faces up to 15 years in jail, although Judge Thokozile Masipa may suspend the sentence or impose a fine.

She said the athlete had acted "negligently" when he shot his girlfriend through a toilet door, but in the "belief that there was an intruder".

The Paralympic sprinter had strenuously denied murdering Ms Steenkamp after a row on Valentine's Day last year, saying he shot her by mistake.

Ms Steenkamp, a 29-year-old model and law graduate, was hit three times by bullets shot through a toilet door by Pistorius at his home in the capital, Pretoria.

Pistorius' personal psychologist Lore Hartzenberg told the courtroom on Monday that Pistorius was "very emotional" during grief therapy sessions, which were often disrupted by his weeping and crying.

She said the athlete felt "vilified and humiliated" by the media and social media networks, making him feel "utterly worthless".