The police were banging on the doors and the windows of her home while she cowered in the closet, a 17-year-old girl recounted. She remembered clutching her phone, crying, calling her mother.

“I was scared,” she wrote of the experience.

It may sound like a drug raid, or the climax of a movie. But in fact, the police, along with representatives of Connecticut’s Department of Children and Families, had come to take the girl for chemotherapy.

The girl, identified in court papers as Cassandra C., learned that she had Hodgkin’s lymphoma in September. Ever since, she and her mother have been entangled in a legal battle with the state of Connecticut over whether Cassandra, who is still a minor, can refuse the chemotherapy that doctors say is likely to save her life. Without it, the girl’s doctors say, she will die.

“It’s poison,” Cassandra’s mother, Jackie Fortin, said of chemotherapy in an interview on Friday. “Does it kill the cancer? I guess they say it does kill the cancer. But it also kills everything else in your body.”