A woman who served 43 years for a murder she did not commit has been released after her conviction was overturned.

Sandra Hemme was 20 years old when she was found guilty of stabbing to death library worker Patricia Jeschke from St Joseph, Missouri, in November 1980. She was given a life sentence.

There was no evidence that linked her to the crime other than a confession she gave under heavy sedation in a psychiatric hospital, a review into her case found.

Now 64, she is believed to have served the longest known wrongful conviction of a woman in US history according to her representatives.

Her legal team at the Innocence Project said they are grateful that Ms Hemme is finally reunited with her family, and they will “continue to fight” to clear her name.

While she is no longer incarcerated, her case is still being reviewed.

Circuit Court Judge Ryan Horsman’s original 118-page ruling overturning her conviction came on 14 June. It said Ms Hemme’s lawyers had clear proof of her innocence, including evidence that was not given to her defence team at the time.

"This court finds that the totality of the evidence supports a finding of actual innocence," Judge Horsman concluded.

The review found that local police ignored evidence that directly pointed to one of their own officers - Michael Holman – who later went to prison for another crime and died in 2015.

Holman’s truck was seen in the area the day of the murder, his alibi could not be corroborated, and he used Patricia Jeschke’s credit card after claiming he found it in a ditch.

A pair of distinctive gold earrings identified by Ms Jeschke’s father were also found in Holman’s home.

None of this was disclosed to Ms Hemme’s defence team at the time, the review said.

Ms Hemme was interrogated by police several times under the influence of antipsychotic medication and a powerful sedative after being involuntarily committed to a psychiatric hospital. She had been receiving occasional psychiatric treatment since she was 12 years old.

Her responses were “monosyllabic” and she was “not totally cognisant of what was going on”, court documents showed, and at times could barely hold her head up straight and was in pain from muscle spasms – a side effect of the medications.

Judge Horsman’s review noted that no forensic evidence linked Ms Hemme to the murder. She had no motive and there were no witnesses linking her to the crime.

Sandra Hemme finally left prison on Friday, and the Kansas City Star reports that she will live with her sister.

After her release, she was reunited with family in a nearby park, where she hugged her sister, daughter and granddaughter.

Her father had been hospitalised and was receiving palliative care this week. Her legal team said she was planning to visit him as soon as she can.

Defence lawyer Sean O’Brien told the Star that she will still need help because she has spent most of her life in prison and was ineligible for social security.