THE lawyer representing the family of Sheku Bayoh, who died in police custody, have said that the force's watchdog has "failed" to use its powers to hold the organisation to account.

Mr Bayoh's relatives will meet the Police Investigations and Review Commissioner (Pirc) Kate Frame on Thursday to discuss the case of the 31-year-old, who died after being restrained by officers in Kirkcaldy, Fife on May 3.

A post-mortem examination proved inconclusive and a Sunday newspaper reported family concerns that experts called in by investigators may blame a medical condition known as excited delirium, which has been cited in other custody deaths.

Ms Frame has said she understands the need for answers around the death and wants to hear any additional information from his partner Collette Bell and family they think might be relevant to the investigation.

However, Aamer Anwar, the lawyer who is representing Mr Bayoh's relatives, said: “It is clear to the family that PIRC has failed to use the powers it has to hold Police Scotland to account.

"Over 17 weeks PIRC has been responsible for the rapid breakdown in confidence held in them by Sheku Bayoh’s family.

"Whilst 53 separate points of concerns were raised in a letter to the Commissioner on 31st July 2015, the family felt her response was dismissive; those concerns were subsequently taken up by the Lord Advocate.

"The Scottish Government has announced a national review into Police Scotland, but the family feels that unless the police watchdog PIRC is truly independent and armed with increased powers then any exercise into police accountability will be one of fruitless window dressing."

He added that the meeting was expected to be "robust and difficult". "The family welcome the opportunity to discuss their concerns with the Commissioner," he said.

The Pirc has said the fact that forensic pathology experts from outside Scotland have been contacted is not a sign that it has focused its investigation on a particular cause of death and that all lines of inquiry are being explored to establish the circumstances.

Ms Frame said earlier: "I fully recognise the family's need for a clear understanding of what caused Sheku Bayoh's death, and despite the fact that the post-mortem conducted shortly after his death was inconclusive, I remain committed to thoroughly investigating all lines of enquiry."

The family of Mr Bayoh, a trainee gas engineer and father-of-two, met the Lord Advocate Frank Mulholland to discuss the investigation last week.