A inmate found to have killed her husband has been handed an unlikely reprieve after it was found prosecutors paraded her thong in court and made a point to dissect her sex life.

Brenda Andrew, 61, was convicted in 2004 for the fatal shooting of her husband Rob Andrew over an insurance payout. She was handed the by jurors after what her defending lawyers said was an attempt by prosecutors to "humiliate and dehumanise" her, and what an Oklahoma judge said was an effort to "trivialise the value of her life".

Campaigners have long asserted that Andrew, who has maintained her innocence, was the victim of legal misogyny, and that prosecutors used her sex life to vilify her throughout the trial and into closing arguments - at one point parading her thong in front of jurors. judges have now delivered a legal smackdown on the tactics used by the prosecution, and spared her from the ultimate punishment.

The US Supreme Court ruled in 7-2 in Andrew's favour this week, finding in an unsigned opinion that prosecutors spent "significant time" focusing on evidence relating to her "sex life and about her failings as a mother and wife". The court concluded the details were used to "dehumanise" Andrew by "denigrating" her to the jury.

The ruling said: "Among other things, the prosecution elicited testimony about Andrew's sexual partner's reaching back two decades; about the outfits she wore to dinner or during grocery runs; about the underwear she packed for vacation; and about how often she had sex in her car.

"In its closing argument, the prosecution again invoked these themes, including by displaying Andrew's 'thong underwear' to the jury, by reminding the jury of Andrew's alleged affairs during college and by emphasising that Andrew 'had sex on [her husband] over and over and over' while 'keeping a boyfriend on the side.'"

Lawyers representing Andrew argued that prosecutors in the initial trial had worked to obtain a conviction and death sentence "by denigrating her character as a woman", and using "sex-based stereotypes". In doing so, prosecutors portrayed Andrew as "immoral, remorseless, deviant, dangerous", and "more deserving of the ultimate punishment", they added.

To illustrate their point, the lawyers said a prosecutor referred to Andrew as a "slut puppy" in their closing argument, and showed off underwear she packed for a trip to Mexico with her boyfriend James Pavatt days following her estranged husband's murder. Withdrawing the thong, the prosecutor reportedly "drew gasps" from the court.

The convincing ruling from the Supreme Court will force a lower court to reconsider her death penalty conviction, and her attorney Jessica Sutton has said she hopes the court, the 10th Circuit Court of Appeals "will stop this injustice".