A Missouri woman has spent 43 years in prison for a grisly 1980 murder that her lawyers say was actually committed by a police officer with ties to the murder scene.

Now, Sandra Hemme is waiting to learn if she’ll regain her freedom, after a judge overturned her conviction last week. He ruled Hemme was in a “malleable mental state” when investigators questioned her in a psychiatric hospital under heavy medication, and that prosecutors withheld evidence about the discredited officer, who died in 2015.

Hemme’s legal team at the Innocence Project say this is the longest time a woman has been incarcerated for a wrongful conviction. The family is ecstatic. “We just can’t wait to get her home,” Hemme’s sister, Joyce Ann Kays, said Monday.

Here are some things to know about the case:

What are the key points?

Judge Ryan Horsman ruled late Friday that attorneys for Hemme had established evidence of actual innocence and that she must be freed within 30 days unless prosecutors retry her.

Hemme was a psychiatric patient when she incriminated herself in the death of 31-year-old library worker Patricia Jeschke. Hemme is now 64 years old and is incarcerated at a women’s prison northeast of Kansas City.

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Hemme’s attorneys have filed a motion seeking her immediate release.

What happens next?

County prosecutors have 30 days to determine whether to dismiss the charges or try her again. The Missouri attorney general’s office can also decide to get involved, Karen Pojmann, communications director for the Missouri Department of Corrections, said in an email.

In the past, exonerated people have been released if there are no plans to appeal the decision or re-try the case, and the Department of Corrections gets that in writing from all the parties involved, Pojmann said.

The Buchanan County prosecutor and a spokesperson for the state attorney general’s office didn’t immediately return phone and email messages from The Associated Press seeking comment.

What happened in 1980?

It started on Nov. 13 of that year, when Jeschke missed work. Her worried mother climbed through a window at her apartment and discovered her daughter’s nude body on the floor, surrounded by blood. Her hands were tied behind her back with a telephone cord and a pair of pantyhose wrapped around her throat. A knife was under her head.

The brutal killing grabbed headlines, with detectives working 12-hour days to solve it. But Hemme wasn’t on their radar until she showed up nearly two weeks later at the home of a nurse who once treated her, carrying a knife and refusing to leave.

Police found her in a closet, and took her back to St. Joseph’s Hospital — the latest in a string of hospitalizations that began when she started hearing voices at age 12.

She had been discharged from that very hospital the day before Jeschke’s body was found, showing up at her parents house later that night after hitchhiking more than 100 miles (160 kilometers) across the state. The timing seemed suspicious to law enforcement.

What are the concerns about the interrogation?

As the questioning began, Hemme was being treated with antipsychotic drugs that had triggered involuntary muscle spasms. She complained her eyes were rolling back in her head, the petition said.

Detectives noted Hemme seemed “mentally confused” and not fully able to comprehend their questions. She offered what her attorneys described as “wildly contradictory” statements, at one point blaming the murder on a man who couldn’t have been the killer because he was at an alcohol treatment center in another city at the time.

Ultimately, she pleaded guilty to capital murder in exchange for the death penalty being taken off the table. That plea was later thrown out on appeal. But she was convicted again in 1985 after a one-day trial in which jurors weren’t told about what her current attorneys describe as “grotesquely coercive” interrogations.

Who do Hemme’s lawyers say is the real killer?

Her attorneys argue that evidence was suppressed implicating Michael Holman, a police officer at the time in St. Joseph, a city on a bend in the Missouri River roughly 50 miles (80 kilometers) north of Kansas City.

About a month after the killing, Holman was arrested for falsely reporting his pickup truck stolen and collecting an insurance payout. The same truck had been spotted near the crime scene, and his alibi that he spent the night with a woman at a nearby motel couldn’t be confirmed.

Furthermore, he had tried to use Jeschke’s credit card at a camera store in Kansas City, Missouri, on the same day her body was found. Holman, who was ultimately fired, said he found the card in a purse in a ditch.

During a search of Holman’s home, police found a pair of gold horseshoe-shaped earrings in a closet, along with jewelry stolen from another woman during a burglary earlier that year.

Jeschke’s father said he recognized the earrings as a pair he bought for his daughter. But then the four-day investigation into Holman ended abruptly, and many of these uncovered details were never given to Hemme’s attorneys.

Why did the judge decide to free Hemme?

Horsman found her trial counsel was ineffective and prosecutors failed to disclose crucial evidence that would have aided in her defense, including Holman’s criminal conduct.

The only evidence tying Hemme to the killing was her “unreliable statements,” Horsman wrote, and her psychiatric condition was “fertile ground for her to also internalize, or come to believe, the apparently false narratives she told.”

He said her statements were also contradicted by physical evidence and accounts of reliable, independent witnesses. The judge said outside factors like media coverage and police suggestion “substantially undermine the prosecutor’s argument that Ms. Hemme’s statements contain details that only the killer could know.”

There was, however, evidence that “directly ties Holman to this crime and murder scene,” he wrote

Were other mentally ill patients questioned like this?

Lawyers at the Innocence Project say Hemme wasn’t the first mentally ill person targeted by detectives in St. Joseph. Melvin Lee Reynolds, who also spent time at St. Joseph’s State Hospital, falsely confessed to the 1978 killing of a 4-year-old boy following repeated interrogations.

He was exonerated and freed in 1983, when a self-proclaimed serial killer, Charles Hatcher, pleaded guilty to the murder.