A mother who died after being set on fire by her boyfriend will testify in court from beyond the grave following a landmark ruling.

The video testimony of Judy Malinowski will be played by prosecutors during the murder trial of her ex-partner Michael Slager, an Ohio judge said on Friday.

Ms Malinowski died in June 2017, aged 33, two years after she was left with catastrophic burns after her boyfriend doused her in petrol and set her alight on a petrol station forecourt in Gahanna, near Columbus.

Slager, 42, was convicted of aggravated arson and felony assault in December 2016, but prosecutors began preparing a murder case against him after doctors said the mother-of-two would not survive her injuries.

As part of their work, they recorded Ms Malinowski’s sworn testimony from her hospital bedside in January 2017, compiling almost two hours of footage

They have now secured the right to play the video in court, a decision that will set a precedent for future criminal trials in Ohio.

Ruling the testimony should be heard, Judge Guy Reece said it was the first case he was aware of where a victim had given evidence at their accused killer’s trial.

“The state wanted to preserve her testimony due to her fragile medical condition,” he said.

Michael Slager faces a murder charge following Ms Malinowski’s death (WBNS-10TV/screen grab)

“She was critically ill and was the only witness who could testify about the events that transpired on the day of her injury.”

The attack left Ms Malinowski with burns covering 80 per cent of her body. She also lost both her ears, two fingers and much of her hair.

She also struggled to talk as a result of injuries to her trachea and resorted to communicating using whispers and nods.

Bonnie Bowes, Ms Malinowski’s mother, said her daughter had always believed her testimony would have been used in court.

“To me, it was whether or not Judy’s voice was going to be heard,” she told Columbus news station 10 TV.

“Judy went through this traumatic experience and she went to her grave thinking that the judicial system would unseal her side of the story.

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“So it was really important to me that that happens.”

Slager has always maintained he never intended to set Ms Malinowski on fire and did so by accident while lighting a cigarette.

His trial is set for July, when prosecutors will be seeking the death penalty.

Video: Judy Malinowski, Set on Fire by Ex-Boyfriend, Dies