A FORMER heroin addict jailed for murdering her toddler son has been cleared after judges at the Court of Appeal criticised a catalogue of errors in the case against her.

Kimberley Hainey, 38, sobbed as her conviction for the murder of son Declan, whose mummified remains were found at home in Paisley in March 2010, was quashed by the Court of Appeal in Edinburgh.

In the appeal ruling, Lord Clarke said the trial judge, Lord Woolman, had clearly failed to follow the instructions given by the appeal court in a previous case of a mother convicted of killing her baby.

He said the judge also failed to focus the jury's attention on natural explanations for Declan's death put forward by defence experts.

Lord Clarke criticised the two prosecution witnesses' lack of medical qualifications, describing the experts from Dundee University as quack doctors.

The investigation of Declan's skeleton, by the university's forensic anthropologist Professor Susan Black and Dr Craig Cunningham, a lecturer in anthropology, found so-called "Harris lines" on his bones and erosion of his cortex which were said to prove malnutrition and maltreatment before he died.

Lord Clarke added: "We have found this to be a particularly anxious and troubling case and we have little doubt the jury would have found it to be so also. There is scarcely any more serious charge than one of murder by a mother of her infant child."

He said such a case must require the most careful and sensitive consideration by prosecutors.

He added: "Putting matters colloquially, it cannot be right for a trial judge to allow an obvious 'quack' doctor to speak to a subject in a supposed expert way in relation to which he has no qualifications."

Ms Hainey's legal team launched an appeal against her conviction after she was jailed for life, with a minimum tariff of 15 years for killing Declan at their home in Bruce Road, Paisley, on the grounds that crucial evidence against her was flawed.

Declan, who would have been 23 months old when he was found, had been left for long periods without food or drink. Meanwhile, the mother partied, drank and took drugs.

Ms Hainey had also been given a seven-year prison sentence for trying to cover up the murder.

Lord Clarke, sitting with Lord Mackay of Drumadoon and Lord Drummond Young, found there had been a miscarriage of justice.

The original trial, which ended in December 2011, heard the post-mortem examination of the child proved inconclusive and that the cause of death was "unascertained".

At her appeal, Ms Hainey's lawyers argued the Dundee University witnesses were anthro- pologists whose expertise could be applied to determining a possible age of the child when he died, but not his condition prior to death.

The judges found the jury was misdirected by the trial judge who did not tell them to ignore any of the evidence given by the forensic scientists.

As a result of the evidence from the two experts and the misdirection from the trial judge, the appeal court quashed the murder conviction.

The judgment also highlighted concerns over whether the jury had been given enough direction from the judge to decide if neglect by Ms Hainey had caused Declan's death.

It said the Crown should ensure that any expert called should be qualified in the specific area on which they are to give evidence.

A spokesman for Dundee University said: "Both Professor Black and Dr Cunningham are qualified forensic anthropologists and gave evidence on that basis. We note the decision of the Appeal Court."

A Crown Office spokesman said: "In January 2012, Crown Counsel instructed that a Fatal Accident Inquiry (FAI) into the tragic circumstances surrounding the death of infant Declan Hainey should be held at the conclusion of criminal proceedings.

"The procurator-fiscal will now apply to the sheriff court to hold an FAI."

The authorities have since implemented the recommendations of a Significant Case Review.

l Lord Clarke's reference to the earlier miscarriage of justice was that of Edinburgh mother Jennifer Liehne, who was cleared of culpable homocide in May 2011. She had been serving seven years in prison for causing the death of her baby daughter Jacqueline in December 1982. She had been initially accused of murder in 2006.