NASHUA, N.H. (AP) — A New Hampshire woman is preparing to plead guilty in the death of her 5-year-old son, according to court documents.

Danielle Dauphinais, 38, will plead guilty Thursday to second-degree murder and two counts of witness tampering in the death of her son Elijah Lewis, according to a plea agreement filed Monday. She faces up to 55 years in prison.

The child was discovered missing and found dead in October 2021 in a Massachusetts park. An autopsy showed he suffered facial and scalp injuries, acute fentanyl intoxication, malnourishment and pressure ulcers.

Dauphinais’ boyfriend, Joseph Stapf, pleaded guilty to manslaughter, second-degree assault, falsifying physical evidence and witness tampering in 2022 in connection with the boy’s death. He was sentenced to 22 to 45 years in prison.

Prosecutors said Elijah was starved, neglected and physically abused. During Stapf’s sentencing, they read a series of texts between Stapf and Dauphinais that expressed hostility toward Elijah.

When Elijah died and child welfare workers started to investigate his disappearance, the couple put his body in a container and brought him to Ames Nowell State Park in Abington, Massachusetts, where Stapf dug a hole and buried him, according to prosecutors.

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Prosecutors said that when Elijah was found, he was 3 feet (0.91 meters) tall and weighed 19 pounds, while an average 5-year-old boy would be about 3.6 feet (1.1 meter) tall and closer to 40 pounds.

When Elijah was still missing, Stapf and Dauphinais were arrested in New York on charges of witness tampering and child endangerment. Days after their arrest, Elijah’s remains were found.

Dauphinais was indicted in 2022 on one count of first-degree murder alleging that she purposely caused her son’s death, one count of second-degree murder alleging she acted recklessly in causing his death, and three counts of witness tampering.

She had initially pleaded not guilty before opting to change her plea.