Experts from across the country are to be drafted in to help investigate the death of Kirkcaldy man Sheku Bayoh.
More tests will be carried out on the 31-year-old after a post mortem failed to establish a cause of death.
The father-of-two collapsed after being detained by police on May 3 and mystery still surrounds the circumstances of his death.
His family fears he may have been the victim of positional asphyxiation after he was restrained by several officers using batons and CS spray.
The police claim officers responded to reports of a man wielding a knife and restrained him when he became violent an allegation disputed by the Bayoh family.
The police watchdog leading the inquiry confirmed the results of the post mortem had been received.
A spokesman for the Police Investigations and Review Commissioner (PIRC) said: “We cannot comment on the detail of the report as this remains a live investigation, but can confirm that further investigation is required in relation to the cause of death and will continue to work closely with the Crown Office to identify experts who can assist in the ongoing investigation.”
The Bayoh family will also instruct their own experts to help with the case.
Aamer Anwar, the solicitor acting on their behalf, said specialists in restraint techniques and positional asphyxia would be called upon.
Renowned pathologist Dr Nat Carey, who was involved in the Hillsborough inquiry and the investigation into the Soham murders, has previously been instructed by the family.
“We are also looking to see if there are others who can bring expertise to this inquiry,” said Mr Anwar.
“The concerns of the family remain the same regarding the police officers who detained and restrained Sheku Bayoh.
“Was the force they used legitimate, reasonable and proportionate?”
An expert from deaths in custody is due to meet Mr Bayoh’s partner Collette Bell and other family members next week.
The family is also seeking another meeting with the Lord Advocate.