Was Woolmer drugged with snake venom?

A friend of the family said Gill Woolmer has been informed that her husband was probably subdued by a 'natural toxin' which left his body by the time of the forensic examination.

Neil Manthorpe, a respected South African and BBC World Service cricket commentator, said: "I spoke to Gill and her sons Russell and Dale two days ago. The boys both said police had told their mum the toxicology results are inconclusive.

"The detective told Gill they believe it must have been a natural poison, such as a snake venom, which leaves the body fairly soon afterwards. The police theory is that this was administered to Bob in the bathroom of his hotel room to subdue him before he was strangled.

"The officer said that the only way to prove this was to look for tissue damage, which was why they had sent the results back to England for further testing."

Police are not working on the theory Woolmer was bitten by a snake, as there are no venomous snakes in that part of the Caribbean. Instead the suspicion is he was injected with venom.

David Warrell, Professor of Tropical Medicine and Infectious Diseases at Oxford University, who has helped police in a number of international murder inquiries, said the vomit and faeces found near Mr Woolmer's body were consistent with someone with venom in their bloodstream.

He added: "Snake venom cannot be slipped to someone in a drink or food. It also cannot be injected into any part of the body.

"It has to go directly into a vein, meaning this man would have had to have been held down for the 20 minutes or so it would have taken for paralysis to set in."

The development came as detectives refused to comment on reports that a suspect has been captured on CCTV cameras at Kingston's Pegasus Hotel, where Mr Woolmer was staying. Jamaican police sources, however, dismissed the claim.

Mr Woolmer's widow Gill is showing signs of losing patience with the inquiry. Speaking from her Cape Town home, she said: "Mark Shields [the detective in charge of the investigation] speaks to me most days and says I can have access to him 24/7, but I feel I don't know what's really going on. I'm fed up with all the speculation."

In Jamaica, Mr Shields has dismissed claims that Mr Woolmer was poisoned with aconite, derived from the plant wolfsbane, saying: "It is not part of our investigation."