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A former Texas nurse suspected in the killing of dozens of children pleaded guilty Thursday in the 1981 death of an 11-month-old boy, receiving a life sentence that a prosecutor said should ensure she dies in prison.

Genene Jones, 69, was imprisoned in 1984 for killing one child and giving an overdose to another.

She had been set for release in 2018 under a mandatory release law that was in place when she was convicted. But prosecutors in 2017, citing new evidence, filed five new murder charges against her related to the deaths of children in the early 1980s.

Genene Jones, a Texas nurse who is in prison for the 1984 killing of a toddler. Texas Department of Criminal Justice / AP file

“With this plea, the odds are she will take her last breath in prison,” prosecutor Catherine Babbitt said after the hearing in San Antonio.

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Children died of unexplained seizures and other complications when Jones worked at a San Antonio hospital and clinic in Kerrville, about 55 miles (90 kilometers) northwest of San Antonio.

Prosecutors at Jones' 1984 murder trial said she had injected children with drugs to demonstrate the need for a pediatric intensive care unit at a nearby hospital. Other prosecutors had theorized that her tactic was to take swift medical action and save some of her victims so she could appear to be a sort of miracle worker.

But Babbitt said in an interview after the hearing that they never determined what Jones' motivation was. "I can only speculate. I mean, I never came across anything that would tell me why she committed such evil acts,” she said.

Jones, who had been set for trial in February, was sentenced Thursday in the death of Joshua Sawyer, who investigators say overdosed on an anti-seizure drug. The other four cases were dismissed, prosecutors said.

Jones will be eligible for parole in 18 years, when she's about 87, Babbitt said.

Several family members gave victim impact statements at the hearing, including Joshua's mother, Connie Weeks.

“I hope for you to live a long and miserable life behind bars. Goodbye,” Weeks said to Jones.

She was sentenced in 1984 to 99 years in prison in the killing of 15-month-old Chelsea McClellan. Later that year, she was sentenced to 60 years in prison in the sickening of 4-week-old Rolando Santos, who recovered. Chelsea was given a fatal injection of a muscle relaxant and Rolando received a large injection of a blood thinner.

In 2017, she was charged in Joshua's death; the 1981 killing of 2-year-old Rosemary Vega; the 1981 killing of 8-month-old Richard “Ricky” Nelson; the 1982 killing of 4-month-old Patrick Zavala; and the 1981 killing of 3-month-old Paul Villarreal.

“We trust our nurses — our nurses are specifically trained to provide comfort and medical care for their patients," Babbitt said after the hearing. “And these patients were not only children, but they were often critically ill children. And for her to decide on her watch who lived and who died is nothing short of evil.”

In 2017, then-Bexar County District Attorney Nico LaHood said Jones may have killed up to 60 children. Babbitt said that as they prepared for trial that prosecutors felt Jones could have been responsible for about 20 deaths. But it's possible no one but Jones will ever know how many children she killed or injured, Babbitt said.