State's most violent inmate is too dangerous to be released from prison.

The most violent inmate in the NSW prison system will remain behind bars after the state government successfully applied to keep her there.

Rebecca Butterfield, 41, will stay locked up for at least another five years, after the Supreme Court ruled she was too dangerous to be released, according to the Daily Telegraph.

It’s the longest she can be kept without re-offending, given she’s reached the end of her 12 year sentence — manslaughter for stabbing another inmate, unprovoked, 33 times.

The attack makes up only one incident in Butterfield’s violent history spanning more than two decades.

She has a been diagnosed with several personality disorders and is known to use self-harm to lure officers into her cell so she can attack them.

She has cut her own throat four times, set fire to her cell severely burning herself and on one occasion headbutted a wall more than 100 times to crack open her own skull.

“There is evidence that some of the defendant’s threats of self-harm or engagement in self-harm are premeditated for the purpose of forcing officers to enter her cell and enabling her to increase her opportunities for violence against the officers,” Justice Stephen Rothman wrote about his decision to keep the suicidal woman off the streets.

“The combination of disorders and psychoses suffered by the defendant and her history of criminal violence leads inexorably to the view that if unsupervised this defendant would more likely than not commit a serious violence offence.”

Butterfield has been the subject of almost 40 Corrective Service alerts in less than a decade and once stabbed an officer in the face as well as throwing urine and boiling water on two others.

She was first convicted in 1996 for relatively minor offences but her crimes escalated until she eventually stabbed a neighbour five times when she tried to stop her from self-harming.