The mother of Nixzmary Brown testified yesterday that police detectives threatened her into writing a false confession in the beating death of her daughter.

Nixzaliz Santiago sobbed and covered her face with her hands several times during a pre-trial hearing, as defense attorneys argued that the written confession, as well as a videotaped statement, should not be admitted as evidence in the case.

During questioning, Ms. Santiago said detectives forced her to implicate herself in the 7-year-old’s death by yelling at her and telling her she would never see her other children again if she did not comply. Ms. Santiago and her husband, Cesar Rodriguez, are both charged with murder in Nixzmary’s death in January 2006.

Through a translator, Ms. Santiago said yesterday that she obeyed detectives because “I felt very sad and very afraid because I thought I’d never see my children again.” The written confession, in Ms. Santiago’s handwriting, was not her own version of events and was dictated to her by detectives, she said.

Ms. Santiago’s tempered flared during the cross-examination, however, when a prosecutor from the Brooklyn district attorney’s office, Ama Dwimoh, asked her to demonstrate the volume of the detective’s voice when he screamed at her during questioning last year.

For the most part, though, Ms. Santiago tearfully made her way through her written statement from the day Nixzmary died, pointing out erroneous passages. Specifically, she said, she ran immediately to help her daughter, and she said she never saw Mr. Rodriguez dunk Nixzmary’s head repeatedly under water in the bathtub of their Brooklyn apartment.

Ms. Santiago further said she tried to help Nixzmary when Mr. Rodriguez tied her up.

“When he would tie my daughter, behind his back I would go and sneak and get my daughter out. My daughter was really good and she doesn’t deserve that,” she said.

“I agree,” Ms. Dwimoh said.