The pathologist who carried out post-mortem tests on the two babies of Sally Clark has been found guilty of serious professional misconduct.
Dr Williams examined both of Mrs Clark's sons
The General Medical Council has banned Dr Alan Williams, 58, of Cheshire, from undertaking court work for three years.
Dr Williams was alleged to have botched post-mortem examinations on Mrs Clark's children in 1996 and 1998. She was wrongly convicted of their murder.
He has repeatedly denied serious professional misconduct.
Dr Williams was also accused of not disclosing evidence that could have helped clear Mrs Clark, who was wrongly convicted of the murders of 12-week-old Christopher and his eight-week-old brother, Harry, in 1999.
Mrs Clark, a solicitor from Wilmslow, had always denied smothering her first son, Christopher and shaking Harry to death.
She was cleared by the Court of Appeal in 2003.
At first, Dr Williams said Christopher had died of a lung infection, but changed his mind after Harry's death, and claimed he was smothered.
He told Mrs Clark's murder trial that Harry appeared to have been shaken to death but he did not keep proper records of tests he carried out, throwing doubt on the quality of his work, the GMC had heard.
Microbiology results from Harry's post-mortem examination suggested he may have died from an infection with a bacterium called staphylococcus aureus, but Dr Williams did not disclose this at Mrs Clark's committal, to the police or to the Crown Prosecution Service.
The Fitness to Practice Panel considered the facts of the case and ruled that Dr Williams, of Plumley, Cheshire, was guilty of misconduct.
He will not be allowed to do any Home Office pathology work or coroners' cases for the next three years.
Delivering the GMC verdict, chairman Peter Richards said: "In evidence to the panel you agreed that those test results might possibly have assisted the defence.
"Whatever your own views, even if reasonable, you had a responsibility as an experienced forensic pathologist.
"A fair trial hinged on your evidence. Your errors and omissions were formidable," he said.
Dr Williams told the panel he had not considered the tests to be relevant and said if experts for the defence had wished to see them they should have asked for them.
He is currently off work from his job as a consultant histopathologist at Macclesfield General Hospital and has issued no statement in response to the GMC's decision.
Sally Clark was freed in January 2003
In a statement, East Cheshire NHS Trust, which manages the hospital, said: "As a trust we are concerned to learn through the GMC hearing of Dr Williams' failure adequately to carry out his duties as a Home Office pathologist.
"The trust accepts the findings of the GMC and has noted the conditions imposed on Dr Williams' work."
Mike Mackay, Sally Clark's solicitor, said: "I can't see any basis on which following these findings anyone ever would want to rely on Dr Alan Williams again.
"A fundamental requirement of an expert witness is to give objective evidence in an effort to assist the court rather than assist one side or the other."
Helena Kennedy QC, who headed up a working group that looked into how to deal with sudden infant deaths, told the BBC about the recommendations it had put forward to try to ensure such cases did not happen again.
She said: "Experts should be properly trained and understand that they have to be independent and not suborned by one side or the other."
And former Tatton MP Martin Bell, who made the original complaint against Dr Williams, said justice had been done.