PORTLAND — The mother of a 4-year-old boy who died while in the care of foster parents in Durham has filed a damage suit claiming that foster mother Deborah Wolfenden intentionally beat the child to death.

Pamela Miller’s suit, filed Wednesday in Superior Court, also charges that Mrs. Wolfenden’s husband was negligent for failing to stop his wife from battering the boy.

The suit claims that on Jan. 6, Mrs. Wolfenden “did intentionally, willfully, maliciously, wantonly and with a depraved indifference to human life injure Richard LeTourneau III to an extent which resulted in his death.”

The boy, who was taken to a Brunswick hospital, choked to death on his vomit in the Wolfendens’ home after striking his head and suffering a concussion. Mrs. Wolfenden has admitted that she pushed the boy to the floor just before he struck his head and lost consciousness, police said.

In March, the state charged the woman with assault, a decision that enraged many area residents who questioned why Mrs. Wolfenden was not charged with manslaughter.

Officials in the state Attorney General’s Office have said a criminal link between the beatings and the boy’s subsequent death cannot be proven. But Ms. Miller’s attorney, Kenneth P. Altshuler of Portland, said he is confident the link can be made in a civil action because the burden of proof is less than it is in criminal cases.