A CRACKDOWN on sectarian chanting among football fans is being undermined by the unreliability of police evidence in court, a leading QC has warned.

Legislation was brought in last season outlawing offensive behaviour at and around matches, and those found guilty of singing offensive songs face a maximum of five years in prison.

But following two cases in which supporters were cleared of the crime after doubt was cast over the evidence of officers involved in their arrest, Brian McConnachie QC has claimed sheriffs are reluctant to convict unless the evidence is clear-cut.

He said the required standard of evidence in such cases was increasingly difficult to reach and doubts about what officers heard could be exploited in court.

Mr McConnachie said: "Evidence to prosecute in these type of cases is a pretty difficult standard to reach. It's all about what police officers or someone else has heard and what a sheriff can say has left him or her beyond reasonable doubt. When you have 50 or 60 people singing the same song and you pull out one person from the crowd, then the opportunity for doubt about what you've heard must be high.

"It's difficult for the police in these situations. They may well have heard what they've claimed but the evidential position is difficult to satisfy."

It came after the case against Celtic fan Kieran Docherty, 20, who was charged with breach of the peace and conducting himself in a disorderly manner, was found not proven. He was alleged to have shouted "Oo Ah up the Ra" – a reference to the IRA – at a match between Celtic and Inverness Caledonian Thistle in February.

But the case fell apart after a police sergeant admitted under cross-examination during the trial that she could not lip read and that nobody except herself had reacted to or been alarmed by the song.

Sergeant Eleanor Murdoch's colleague, Sergeant Ian Spence, was asked how, if he was six metres away from Mr Docherty, he could be certain he could hear the accused singing the song given there were many others singing different words around him. Both officers had been monitoring the travelling support.

Sheriff Halley said he was unable to accept Ms Murdoch's evidence "in some respects", with Mr Spence's contribution described as unreliable.

It follows a rising number of complaints to the procurator-fiscal regarding behaviour at football matches, many of which either fail to reach the court or are dismissed, with few successfully prosecuted.

Rangers fan Connor McGhie was found guilty of behaving in a threatening or abusive manner by repeatedly singing abusive and sectarian songs at a match between his side and Inverness Caledonian Thistle on February 26. The 19-year-old is appealing the three-month sentence he received at Inverness Sheriff Court.

Advocate and human rights expert Niall McCluskey said the scope of the Offensive Behaviour at Football legislation was so wide that it could lead to over-zealous policing.

He added: "Not when we're talking things which are gratuitously sectarian and racist, but at the end of the day you've got to cut a bit of slack with what people can do in that environment.

"The idea that police officers themselves are the offended party is just crazy.

"There are comparisons with the way in which the authorities clamp down on social media - leeway has to be given to general rabble-rousing behaviour."

Mr Docherty, from Greenock, claimed he was singing another version of the offensive line, "Oo ah Samaras" – a reference to Celtic striker Georgios Samaras.

He pleaded not guilty to the allegations.