POLICE are under pressure to release a report on a heavily-criticised forensic investigation into a notorious gangster's death.

The review of evidence-gathering in the investigation of the death of Kevin "Gerbil" Carroll was ordered after a man charged with the murder - in a supermarket car park in Robroyston, Glasgow - was cleared and the trial judge branded a police raid on his home "horrendous".

Ross Monaghan walked free from court in 2012 because of a lack of evidence and amid claims the police had undue influence on the forensic scientists in the case. Lord Brailsford criticised the police raid on Mr Monaghan's home in Penilee, Glasgow, because of possible contamination of evidence.

A report has now been completed on the investigation and the Scottish Police Authority (SPA) - which asked for the review - says it has been advised by the Crown Office to withhold publication as the Carroll case is ongoing.

But Brian McConnachie QC, chairman of the Faculty of Advocates Criminal Bar Association, says the decision makes no sense.

He said: "The report presumably is in relation to the defects in the original examination of these various items of forensic evidence, not a report in relation to finding evidence to prosecute someone now. I can't see how it would impact on any future case."

Mr McConnachie, a former prosecutor, added: "This was a very high-profile trial in which the evidence seems to have fallen woefully short. In the circumstances, the public, not least those with a particular interest in the murder of Kevin Carroll, deserve to know what the position is."

Solicitor advocate John Scott QC said there is an argument for at least a redacted version of the report by the Home Office Forensic Science Regulator to be released.

He argued: "If there's any risk publication could affect future proceedings, then not disclosing it would be the right thing to do.

"However, where a major High Court trial comes to the sort of conclusion that one did, with the judge making public comment on unsatisfactory aspects of the forensics, it's not good enough to leave it to some unclear future date before explaining what went wrong.

"The risk otherwise is that the same problems result in other trials ending in the same way, or worse than that, we end up with a miscarriage of justice."

Campaigner Iain McKie, whose police officer daughter Shirley was at the centre of a major scandal over fingerprint evidence, said it is in the interests of justice for the report to be released.

He said: "The Crown Office and the police need to take steps to ensure evidence is reliable and safe so miscarriages of justice don't happen and it's vital the public are kept informed so we can have confidence in our justice system. The report must be released."

Mr Monaghan was cleared of the killing of Mr Carroll on January 13, 2010, due to a lack of evidence.

Police investigating the murder are still hunting for suspect Billy Paterson, believed to be abroad.

The SPA say the regulator's report will be released when there are no legal impediments, but concerns have been raised that it might never happen if no-one is caught for the killing.

Scottish Conservative justice spokeswoman Margaret Mitchell said: "There is an issue of transparency here, because people need to know what went wrong."

Graeme Pearson, Scottish Labour's justice spokesman, added: "The public deserve answers. We need to know what steps have been taken regarding the regulator's investigation and what was the result."

Tom Nelson, director of SPA Forensic Services, said he was unable to comment on the report now due to the ongoing investigation into the murder.

He said: "I have had sight of the conclusions and recommendations made by the Regulator and have been reassured by them. It has always been my intention to publish the full report when there are no legal impediments to do so and that commitment remains."

The Crown Office refused to comment, and Police Scotland said it was a matter for the SPA.