A Chinese forensic expert said Friday she doubts the official version of what caused the death of a British businessman whose murder touched off the nation's biggest political scandal in decades.

Wang Xuemei, a forensics official with China's national prosecutor's office, told AFP a court's conclusion that the wife of one of China's top politicians poisoned businessman Neil Heywood with cyanide was flawed.

"That our court went so far as to believe the conclusion that cyanide was the cause of death is very distressing, unsettling and scary," Wang said.

Wang noted that she had no direct involvement in the case and did not examine evidence first-hand, but her doubts echo those of many Chinese that the case was being manipulated to minimise embarrassment to the ruling Communist Party.

Gu Kailai, the wife of rising political star Bo Xilai -- former top Communist official in the southwestern municipality of Chongqing -- was sentenced in August to a suspended death sentence that will likely be commuted to life in prison.

The emergence of the case earlier this year triggered the political downfall of her husband, who was seen as a potential candidate for elevation to the top echelons of party power at a Communist Party meeting expected to be held within weeks.

No legal action has yet been taken against Bo.

Wang, who also is deputy director of the Chinese Forensic Medicine Association, said court documents and testimony describing the sequence of events in Heywood's death do not fit with what happens in a cyanide poisoning.

Cyanide poisoning causes immediate asphyxia, spasms and a heart attack and turns the skin and blood bright red, she said, adding that reports on Heywood's death that she has seen do not indicate such symptoms.

"I have serious suspicions over the blood samples that Wang Lijun controlled for three months and then suddenly produced as the fatal poison," she said.

Bo's right hand man, Wang Lijun, who was formerly vice mayor and police chief of Chongqing, was sentenced this week to 15 years in prison for attempting to cover up the murder, as well as other crimes.

The scandal emerged in February when Wang fled to the United States consulate in Chengdu city, apparently fearing for his life after he revealed to Bo that his wife was involved in the murder.

Wang Xuemei, who first aired her doubts in a blog posting that has since been removed by China's censors, refused to speculate on why or how the court reached its conclusion on cyanide.