The Court of Appeal has rejected Sainey Marong’s claim that he was insane when he murdered Renee Duckmanton in May 2016.
Marong, a Gambian-born butcher who lived in Ilam at the time, is serving a life sentence with a minimum 18-year non-parole term for the murder of the 22-year-old who was doing sex work along Manchester Street.
Marong had claimed at the time of the trial that he was insane at the time of the killing, which had involved him strangling Miss Duckmanton and then setting her body alight on a roadside at Rakaia.
He had admitted killing her, claiming he had strangled her as he tried to shut her up when the argued after having sex. The Court of Appeal said the Christchurch High Court jury plainly rejected this account, which might have precluded murderous intent.
After the appeal hearing in October, it released its decision today dismissing the appeal.
The judges said Marong’s internet browsing history indicated that the offence was planned. He had researched kidnapping, information about local sex workers, how to render someone unconscious, necrophilia, and destroying DNA traces by burning a body.
The defence case was that Marong, who is diabetic, had not been taking his insulin and was accordingly likely to be hypoglycaemic, with the result that he did not understand the nature and quality of what he was doing.
Expert evidence about insanity was given by a forensic psychologist and a consultant psychiatrist who were both called by the Crown. Both were firmly of the opinion that Mr Marong was sane. One gave an opinion that Marong was prone to exaggerate symptoms, was histrionic and had a strong propensity to manipulate and deceive, and the other’s opinion was that Marong’s symptoms were likely malingered or fabricated. Nothing about the evidence of his behaviour about the time of the killing suggested that he was in a state of delirium.
At sentencing, the judge sentenced Mr Marong on the basis that the murder was premeditated, and likely committed in pursuit of a depraved sexual fantasy.
The Appeal Court said that the question of whether Mr Marong was in fact insane was for the jury to answer. To succeed on appeal on this ground, he must show that their answer was unreasonable.
The judges stated: “Proof of a disease of the mind usually rests on expert evidence. Mr Marong’s calculated behaviour was plainly abnormal in the extreme, but the only expert evidence about his state of mind was unequivocal; he suffered from no disease of the mind, and was able to understand the nature and quality of his acts and to distinguish right from wrong.”