At least two men believed to have been involved in disposing of drug dealer Stephen Ramon Cookson's body have spoken to police about the head-in-the-bag murder mystery.

Major crime squad detectives confirmed yesterday that the severed head, found on Rottnest Island on January 6, was Cookson's.

_The West Australian _ understands police have interviewed people who came into contact with bags and other property possibly linked to the death of Cookson, 56.

It is unclear whether the men knew what they were dumping or if they were involved in the murder, believed to have occurred at Cookson's rented East Perth apartment.

Confirmation of Cookson's identity comes as _The West Australian _can reveal how Cookson threatened to cut off a woman's head after she complained to authorities that he duped her out of more than $300,000 as part of a deal involving four racehorses.

The woman, who did not want to be named, was confronted by Cookson outside the offices of Perth Racing in 2011 after she went to alert investigators about the fraud.

Her father, Norbert Torney, said his daughter recorded the threatening meeting and the evidence resulted in Cookson being convicted over the threats in November. Charges of fraud were still outstanding.

"You're going to lose your life if you do this," Cookson told the woman in the Perth Racing carpark. "Someone is going to come around and shoot you, knock on your door and put a bullet in your head."

He continued his threats by warning she would lose her property and "I will f . . . . . . dead set cut your head off".

Mr Torney yesterday recounted his family's three years of hell dealing with Cookson while their daughter suffered financially and physically.

"I wish I knew who had done this to Cookson because I would send them a card," Mr Torney said.

But Mr Torney claimed he had to push police to investigate Cookson and even wrote to the AttorneyGeneral demanding action.

After obtaining hundreds of documents and speaking to racing industry people and Perth criminals, Mr Torney believes Cookson was a police informant.

Supposedly Melbourne-born, Cookson used several aliases to dupe unsuspecting horse racing industry operators.

A horse breeder who was managing one of the four racehorses Mr Torney's daughter thought she had bought a share in said yesterday he had been threatened by Cookson, who used the alias Paul Boxall.

Mr Boxall is believed to have been an associate of Cookson and now lives in South Australia.