In this 1998 case -R. v. Patrick Nicholls [1998] EWCA Crim 1918 – a man was convicted of murder and robbery, and served 23 years in prison before having his conviction overturned.
A pathologist suggested that the deceased had been suffocated and suffered heart failure as the result of an assault. He had initially thought she died as the result of natural causes, but then changed his mind.
Subsequently, his view was assessed by two other pathologists who concluded that his final conclusion was wrong. There was also a failure to disclose notes that might have assisted the defence.
Full judgment here: R. v. Patrick Nicholls [1998] EWCA Crim 1918