Image copyright AFP Image caption The mutilated bodies of the two women were found in Mr Jutting's flat in Hong Kong

A British banker accused of killing two women in Hong Kong had been diagnosed with narcissistic personality disorder and sexual sadism, the court has heard.

A medical witness for the defence said Mr Jutting also suffered from the effects of cocaine and alcohol abuse.

Mr Jutting has pleaded not guilty to murdering Sumarti Ningsih and Seneng Mujasih in 2014 on the grounds of diminished responsibility.

He did plead guilty to manslaughter, but the prosecution rejected that.

Defence witness Richard Latham, a consulting forensic psychiatrist in the UK's National Health Service, said Mr Jutting's disorders had progressed to the "most severe end of the spectrum" by the time of the killings.

His ability to control his behaviour was "substantially impaired", Mr Latham said.

Read more: Sumarti Ningsih's story

Mr Jutting's defence lawyer, Tim Owen QC, said that his client had had a troubled upbringing.

He was sexually abused during his boarding school days at the prestigious Winchester College in the UK, and his father attempted to kill himself while he was 16, he said.

At the scene: Helier Cheung, BBC News, Hong Kong High Court

Both the prosecution and the defence agree that Mr Jutting killed Sumarti Ningsih and Seneng Mujasih.

The crux of the argument is Mr Jutting's psychiatric state at the time - and hence, whether he had diminished responsibility or not.

The difference between murder and manslaughter has significant implications for the sentence - a murder conviction leads to a mandatory life sentence, and while the maximum sentence for manslaughter is also life, lower jail sentences are also possible.

The defence witness, Dr Richard Latham, would not say whether he believed Mr Jutting had mental responsibility for his actions or not - but did say that the four mental disorders he had diagnosed Mr Jutting with had substantially impaired his ability to control his behaviour.

Mr Jutting sat calmly in court as the witness gave evidence, surrounded by three police officers. He appeared to be observing proceedings carefully, reading through documents as the court referred to them.

The court has previously been shown videos showing Mr Jutting torturing Sumarti Ningsih, 23.

In other videos filmed on his iPhone, Mr Jutting also takes cocaine, consumes alcohol and explains why he tortures women.

The gruesome details of the murder case has captured international attention. It is the biggest murder trial in Hong Kong in years, as the city is considered one of the safest in the world.