Gambian-born butcher, Sainey Marong has today been found guilty of murdering Christchurch woman Renee Duckmanton.

It took a jury at the High Court in Christchurch just 50 minutes to reach its unanimous verdict.

During the harrowing two-week trial, 33-year-old Marong admitted strangling Duckmanton in May 2016 after picking her up from the city's red light district before setting her body on fire.

But he denied that he meant to kill her, and had no murderous intent, claiming he was insane at the time, suffering mental impairment and delusional, psychotic thoughts which began after voluntarily stopping his insulin medication early in 2016.

The jury, however, sided with Crown and its "overwhelming" evidence, dismissing Marong's claims that he had been "disconnected from reality" at the time he killed Duckmanton, and that from May 6-17, he was poisoned by kidney failure that resulted in urine "travelling in my brain".

A psychiatrist and a psychologist, who both assessed Marong before he stood trial, concluded that he did not meet the criteria for a defence of insanity.

Forensic clinical psychologist Ghazi Metoui found that Marong reported a settled mental state over the period "leading up to, during and subsequent" to the killing.

Dr Erik Monasterio, a forensic psychiatrist, found Marong's claims of insanity to be "farcical" and "preposterous".

His DNA matched samples taken from Duckmanton, and was also directly linked to samples found where her body was dumped.

Marong, whose internet history in the days before the killing showed searches for necrophilia, denied having sex with her dead body.

The jury, however, sided with Crown and its "overwhelming" evidence, dismissing Marong's claims that he had been "disconnected from reality" at the time he killed Duckmanton, and that from May 6-17, he was poisoned by kidney failure that resulted in urine "travelling in my brain".

A psychiatrist and a psychologist, who both assessed Marong before he stood trial, concluded that he did not meet the criteria for a defence of insanity.

Forensic clinical psychologist Ghazi Metoui found that Marong reported a settled mental state over the period "leading up to, during and subsequent" to the killing.

Dr Erik Monasterio, a forensic psychiatrist, found Marong's claims of insanity to be "farcical" and "preposterous".

His DNA matched samples taken from Duckmanton, and was also directly linked to samples found where her body was dumped.

Marong, whose internet history in the days before the killing showed searches for necrophilia, denied having sex with her dead body.

His movements on May 14, 2016 were recorded on CCTV as well as cellphone and bank records.

During his evidence, Marong said that after he had sex with Duckmanton in the back seat of his car, she wanted to return to Manchester St.

He said "that voice, that screaming, that yelling was agitating me" and the dispute "triggered something very serious".

"The only method I could use to stop it was to compress her neck," he said.