CONVICTED murderer Grant Helling committed suicide at Phnom Penh's Monivong Hospital on Saturday.

Thea Nen, a doctor at Monivong Hospital, said the 46-year-old American hung himself with his clothing between 10am and noon Saturday.

"Helling's lawyers, court prosecutors as well as US and prison officials came to inspect the body," he said.

Helling, former policeman, was sentenced to 12 years in prison for killing a 20-year-old Vietnamese prostitute in February this year.

The court held that Helling strangled the prostitute with a coathanger and hid her body beneath his mattress for three days. When he then set the mattress alight, his landlord called the police, and Helling jumped from a first-floor window in an attempt to evade arrest, seriously injuring his leg.

Throughout the court case Helling maintained the death was unintentional.

"It was just like I was driving my car home from work and hit someone and threw the body in a ditch. It was an accident. I've never hurt anyone in my life," he told the Post in March.

Mong Kim Heng, head of administration at Prey Sar Prison in Phnom Penh, said Helling was transferred to Monivong Hospital in August for further treatment to his injured leg.