A US nurse, who killed three patients and tried to kill more than a dozen more at nursing facilities across Pennsylvania, has been sent to life in prison, media reports said.

Attorney General Michelle Henry announced that a western Pennsylvania nurse will spend the rest of her life in prison, without the possibility of parole, for intentionally administering lethal doses of insulin to patients at numerous skilled nursing facilities.

Heather Pressdee, of Natrona Heights, pleaded guilty to three counts of first-degree murder, and 19 counts of criminal attempt to commit murder, read a statement issued by  the Pennsylvania attorney general’s office.

Pressdee, 41, pleaded guilty to avoid the death penalty, her attorney Phillip DiLucente told CNN.

The guilty pleas regard Pressdee administering lethal and potentially lethal doses of insulin to 22 patients at facilities in Allegheny, Armstrong, Butler, and Westmoreland counties, beginning in 2020.

"Most of the patients died very soon after the insulin dose, or some time later, read the statement issued by the Attorney's office.

In accordance with a plea agreement, a Butler County Judge sentenced Pressdee to three consecutive life sentences regarding three counts of first degree murder, plus 380 to 760 years of consecutive incarceration for the 19 counts of criminal attempt to commit murder.

“The defendant used her position of trust as a means to poison patients who depended on her for care,” Attorney General Henry said. “This plea and life sentence will not bring back the lives lost, but it will ensure Heather Pressdee never has another opportunity to inflict further harm. I offer my sincere sympathy to all who have suffered at this defendant’s hands. I commend my agents and investigators, and assisting agencies, who meticulously worked this investigation to uncover the defendant’s terrible acts.”