Police have been cleared of influencing forensic evidence in a collapsed gangland murder trial after a Home Office review.

The first man charged with the gun murder of notorious crime figure Kevin "Gerbil" Carroll in an Asda car park in Robroyston, Glasgow, in January 2010, was acquitted after the judge ruled there was a lack of evidence.

Ross Monaghan walked free from the High Court in Glasgow in 2012 after the trial collapsed. The judge branded evidence linked to the discovery of gun residue as "disturbing". William Paterson has since been convicted and and jailed for life for the murder of Carroll after a trial.

The judge in Mr Monaghan's trial singled out testimony from forensics expert Alison Colley, of the-then Scottish Police Services Authority (SPSA), who claimed she had been put under pressure by a senior officer involved in the investigation.

Lord Brailsford said: "Ms Colley displayed great candour and said she had been told to file her report in the way she did by a detective superintendent.

"I find this evidence to be disturbing. If the integrity of SPSA is to be maintained it should not be influenced by any outside body."

A full review by the Home Office's Forensic Services Regulator (FSR) into the handling of the evidence by police and forensic services at the SPSA, published on Wednesday, found "no attempt was made by the police or management of the SPSA to influence the content of the evidence provided".

As part of the police investigation into the murder a jacket found at Mr Monaghan's home during a police raid was submitted to the forensic science laboratory in Glasgow. Officers requested the jacket be examined for the presence of gunfire residue.

The lab examined and found one particle of discharge residue. It then compared the particle to materials found on cartridges recovered from a number of locations.

Mr Monaghan was prosecuted for the murder of Carroll. He was acquitted as the judge ruled the evidence in relation to the discharge residue was inadmissible.

Ballistics expert Ms Colley said a single particle of gun residue found on a jacket belonging to Mr Monaghan was too flimsy to prove he shot Carroll but she told the High Court in Glasgow that she was still asked to form a conclusion by a detective superintendent.

Lord Brailsford said: "The single particle is of no evidential value. It was absolutely clear the search of the house and the jacket seizure gave rise to contamination.

"I was told the search was, in scientific terms, horrendous, and that is also my conclusion."

The review concluded "the SPSA performed a comparison which would not routinely be performed but which was not prohibited. The comparison was performed at the request of the police and against the advice of the forensic scientists.

"There was nothing inherently wrong in the police requesting the comparison. There was nothing improper in the scientists performing and reporting the comparison.

"The report issued by the forensic scientists, taken in conjunction with the precognition and testimony, provided an accurate statement of the evidence.

"The evidence provided by the SPSA was not, other than reporting comparisons undertaken at the request of the police, affected by the police requests. No attempt was made by the police or management of the SPSA to influence the content of the evidence provided."