EVIDENCE given by two former co-accused in the Lynda Spence murder trial amounts to "a back-shop deal", a defence lawyer has said.

Paul Smith and David Parker's accounts are "tainted" and the result of a "grubby" deal with prosecutors, said Gary Allan QC.

The pair went from being on trial for murder to the Crown's "most credible and publicly minded witnesses", Mr Allan said.

Parker, 38, and Smith, 47, were cleared of killing Ms Spence, a businesswoman who disappeared in April 2011, when they pleaded guilty to a reduced charge of holding her against her will and assaulting her.

Both men have told the High Court in Glasgow–where Colin Coats and Philip Wade, both 42, remain on trial charged with her abduction, torture and murder – that they were offered money to "babysit" the missing woman.

They told how Coats and Wade, who deny the charges against them, would arrive every day to inflict violence on her.

Mr Allan, defending Wade, pointed out that Parker and Smith both tried to plead guilty to a more serious charge eight months ago but it was refused by the Crown.

In his closing speech to the jury, the lawyer said: "Without the accounts of Parker and Smith, the Crown had no evidence whatsoever to provide a narrative to put to you about what happened to Lynda Spence."

The Crown chose to accept the men's guilty pleas "as a last resort" and only when it was "running out of ammunition" which shows a lack of confidence from the Crown in its own case, Mr Allan said.

By their own admission, Parker and Smith would have pleaded to anything to escape the risk of a murder conviction, he said.

"We all know a grubby, back-shop deal was done."

The defence lawyer also asked the jury to consider what Parker and Smith had to gain by pleading guilty to anything other than murder.

The main incentive would have been a far reduced sentence – of up to 20 years less – than if they risked a murder conviction, according to Mr Allan.

Earlier, solicitor general Lesley Thomson QC, prosecuting, finished her closing remarks and invited the jury to convict Coats and Wade of murdering Ms Spence.

Like Mr Allan, she pointed to the evidence given by Parker and Smith.

"What I'm asking you to accept in relation to their evidence is that they provided a truthful account of what happened to Lynda Spence when they were guarding her," she said.

"No one would make up that dreadful tale. No one would make a crime up for the police when no crime had been committed. It makes no sense.

"They have pleaded guilty to a very serious charge and are now facing a very serious sentence."

She also said that if Parker's flat in Meadowfoot Road, West Kilbride, Ayrshire was being used as a safe house, as has been suggested during the trial, more forensic evidence of Ms Spence being there would have been found than just one blood mark in the bathroom.

"There is a clear and compelling case. For the last two weeks of Lynda Spence's life, Colin Coats and his close friend Philip Wade were her jailers, torturers and ultimately her murderers," Ms Thomson said.

"I invite you to conclude that the verdict against these men is one of guilty."

The trial, before Lord Pentland, continues.