CHILLICOTHE, Mo. (AP) — A former respiratory therapist has pleaded guilty in the deaths of two patients at a Missouri hospital two decades ago.

Jennifer Hall, 42, initially was charged with two counts of first-degree murder but pleaded guilty instead Friday to reduced first-degree involuntary manslaughter counts in the deaths of 75-year-old Fern Franco and 37-year-old David Wesley Harper, The Kansas City Star reported. She also pleaded guilty to one count of second-degree assault.

Franco and Harper were among nine patients who died at Hedrick Medical Center in Chillicothe over several months in 2002 in what charging documents describe as “medically suspicious” events.

From December 2001, when Hall started working at the hospital, until she was placed on administrative leave the following May, there also were 18 cardiac arrests or “Code Blue” events, up from an average of one a year before then.

The case was revived after an analysis of Franco’s tissue samples found morphine and a powerful muscle relaxant used in anesthesia in her system. Neither drug was prescribed or ordered for her by her doctors, investigators said.

Some staff at the hospital believed Hall was responsible because of her proximity to the stricken patients, her access to deadly pharmaceuticals, and because she notified staff of every patient’s cardiac emergency, according to court documents.

Hall had previously denied any involvement in the deaths.

Families of patients who died during Hall’s employment later sued the hospital.