For years, Hilda Rosa Dos Santos worked as a domestic for a family in her native Brazil and was treated well, she said. When a member of the family decided to move to the United States in 1979, Dos Santos came along to work for her, her husband and their young son in the couple's Gaithersburg town house.

After her arrival, Dos Santos became a "live-in slave," the victim of beatings and humiliation at the hands of Rene and Margarida Bonnetti for nearly 20 years, prosecutors argued yesterday in the trial of Rene R. Bonnetti in U.S. District Court in Greenbelt.

In a case that federal officials say echoes the plight of thousands of foreign domestic workers who are brought into the United States by their employers and abused, the Bonnettis are each charged with knowingly harboring an undocumented alien, harboring an undocumented alien for financial gain, causing serious bodily injury and endangering the life of an undocumented alien they harbored. Conviction on each of the charges could result in a prison sentence of more than 20 years.

Margarida Bonnetti, 46, is a fugitive. John C. Maginnis, Rene Bonnetti's attorney, said his client knew that Dos Santos's visa was expiring in 1984 and urged her to seek assistance to legalize her status. He said federal authorities have granted Dos Santos legal status and suggested that would affect her testimony.

Speaking through a Portuguese interpreter, Dos Santos, 65, testified to a series of horrific assaults by Margarida Bonnetti.

Bonnetti once poured hot soup on her face and chest because she didn't like the way Dos Santos had prepared the soup, Dos Santos testified. Another time, she testified, Bonnetti became enraged at the way she was combing the hair of the family dog, furious that the dog was losing some hair in the process.

"She yanked so much hair from my head that my head was bleeding," Dos Santos testified.

When she implored Rene Bonnetti to help her, he replied that she should pray for Margarida, Dos Santos testified.

Illiterate in her native language and unable to speak English, Dos Santos couldn't help herself, prosecutors said, until April 1998, when neighbors took her to a hospital for treatment of a large stomach tumor, and social workers learned of her alleged mistreatment.

Prosecutors say the Bonnettis, both originally from Brazil, arranged for a temporary visa so Dos Santos could accompany them to the United States, where the engineer and his wife bought a comfortable brick town house in the Montgomery Village section of Gaithersburg. Then the abuse began, prosecutors allege.

"The evidence you will hear may surprise you, the evidence you will see may shock you," Assistant U.S. Attorney Steven M. Dettelbach said in his opening statement.

The Bonnettis quickly put her to work--having her clean their house, wash windows, rake leaves, cook, and even shovel snow without gloves, boots or a coat--all while never paying her, prosecutors allege.

When the Bonnettis were away, Dos Santos testified, she had a friend scribble cards for her in English and roamed the neighborhood showing the cards to residents, many of whom helped with clothing, shoes or money.

While the couple slept in comfort upstairs, Dos Santos was relegated to a mattress in the basement, Dettelbach said, and was not allowed to share the amenities of the main part of the house. Rene Bonnetti even padlocked the refrigerator to prevent Dos Santos from eating the same food as the family, Dettelbach said.

"The Bonnettis essentially got a live-in slave," Dettelbach said. "Mr. Bonnetti and his family got free work for 20 years."

Maginnis, Rene Bonnetti's attorney, said in his opening statement that Dos Santos was involved in a family squabble in Brazil and that the Bonnettis brought her with them to the United States to help her.

Maginnis said Dos Santos did some domestic work for the family but was such a "spectacularly incompetent housekeeper" that the Bonnettis curtailed her duties until she had virtually nothing to do.

Dettelbach alleged that the Bonnettis did not provide Dos Santos medical care, which endangered her life when a small leg cut became infected. The Bonnettis also refused to provide treatment for a large, visible stomach tumor the size of a soccer ball, Dettelbach said.

"I was so tired of suffering that I wanted to get out of that house and disappear," Dos Santos testified.