A Brooklawn woman admitted Monday to giving her husband's grandmother antifreeze mixed in a drink, ultimately leading to the elderly woman's death, authorities said in a press release.

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Anne Castagna, 45, pleaded guilty Monday to first-degree aggravated manslaughter in the Aug. 19, 2012 death of 88-year-old Mary Groatman.

Castagna admitted to her attorney that on Aug. 19, 2012, she visited Groatman, her husband's grandmother, who was a patient at the Deptford Center for Rehabilitation and Health Care, the Gloucester County Prosecutor's Office said. Witnesses admitted to seeing Castagna at the facility that day.

Hours after her visit, staff members found the elderly woman in a coma. When her condition failed to improvve, Groatman was taken off life support and later died.

According to the Prosecutor's Office, following an investigation, Castagna was arrested on Aug. 23, 2012. Her plea came the day before jury selection was set to begin for a trial.

Assistant Gloucester County Prosecutor Joseph Brook has recommended a plea deal that will sentence Castagna to 25 years in New Jersey state prison, without the possibility of parole for at least 21 years, three months and one day - which is 85 percent of the sentence. The plea deal was accepted by Superior Court Judge M. Christine Allen-Jackson, after receiving approval from the court district’s assignment judge and presiding criminal court judge. The deal was reached quickly as a trial date became imminent and "the normal time to enter a guilty plea had passed," the prosecutor said.

"The original first-degree murder charge was amended to first-degree aggravated manslaughter, the charge to which she pleaded," the prosecutor's office said in a statement Tuesday.

The prosecutor said sentencing for Castagna was scheduled for Feb. 5 and her bail was revoked pending sentencing. She has been in jail in default of $250,000 bail since her arrest.

Toniann Antonelli is the digital managing editor for news at NJ 101.5. Reach her at toniann.antonelli@townsquaremedia.com, or on Twitter @ToniRadio1015.