THE interests of justice are being put at risk by a rule leaving defence lawyers unpaid if their client's case is dropped because of delays, appeal judges have ruled.

Lady Paton urged reform of the way defence lawyers are paid for some cases as she warned a feature of the legal aid system could lead to costly human rights challenges by those accused of crimes.

The development comes after a sheriff decided to throw out charges against two men accused of a serious assault in Edinburgh's Slateford Road two years ago.

Prosecutors went to the Court of Criminal Appeal in Edinburgh to challenge Sheriff Katherine Mackie's ruling that the human rights of the two would be breached because they could not be guaranteed a proper defence, given the fees question.

Sheriff Mackie said there was a "clear inequality of arms" between the defence and prosecution because the lawyers for the accused were expected to prepare for a potentially significant hearing without payment. As a result, the sheriff dropped the case against Darryl McCrossan, 22, and Keith Wilson, 21, both of Edinburgh, accused with others of punching, kicking and stamping on a man in the capital in May 2011.

Lawyers for the two had argued for plea in bar of trial given the time taken to bring the case to a jury trial, with a number of hearings, amendments to the charge and two trial dates being abandoned because a witness was ill. Three separate indictments had been served.

But Lady Paton, sitting with Lord Brodie and Lady Cosgrove, overturned Sheriff Mackie's decision and said trial should go ahead against all seven men accused of the crime, including Mr McCrossan and Mr Wilson.

The sheriff had been "premature" in deciding the accused would not get a fair trial because of the row about fees, the judges said.

But, delivering the ruling yesterday, Lady Paton said there were implications for solemn proceedings, serious criminal cases which involve trial by jury.

She added: "We also observe that it would be an unfortunate and short-sighted policy to maintain the present rigidity in the legal aid regulations relating to solemn criminal proceedings."

She warned: "It seems likely challenges such as the present will be repeated in other cases, at considerable cost to the public purse, possibly bringing to a premature end proceedings which ought properly to be taken to their final conclusion."

Also facing trial are Ryan Todd, 21, James Todd, 20, Connor Wight, 21, Dale Spence, 20 and Craig O'Rourke, 21. The European Convention on Human Rights guarantees free legal aid "when the interests of justice so require".

Defence QC Brian McConnachie told the appeal judges the regulations were "inflexible" - a claim disputed by advocate depute Dorothy Bain QC, for the Crown.

Mr McConnachie pointed out the Scottish Legal Aid Board paid a flat-rate £152 for a lawyer's preparation work, but that would only be paid if a trial went ahead.

The appeal judges heard that in less serious summary cases the rules were different and seen as more flexible.

Mr McConnachie said solicitors for Mr McCrossan and Mr Wilson may attempt to overturn the ruling in the Supreme Court in London, which can hear humans-rights arguments on a criminal case brought in the Scottish courts.