The agency says it has tripled its investigative staff since then, and counts only 165 serious complaints pending. But it stopped posting an e-mail address and phone number for such complaints last year, said Jan Lane, chief of security and integrity, because it lacks the staff to cull the thousands of mostly irrelevant messages that resulted. Immigrants, she advised, should report wrongdoing to any law enforcement agency they trust.

The young woman in Queens, whose name is being withheld because the authorities consider her the victim of a sex crime, did not even tell her husband what had happened. Two weeks after the meeting in the car, finding no way to make a confidential complaint to the immigration agency and afraid to go to the police, she and two older female relatives took the recording to The Times.

Reasons to Worry

A slim, shy woman who looks like a teenager, she said she had spent recent months baby-sitting for relatives in Queens, crying over the deaths of her two brothers back in Cali, Colombia, and longing for the right stamp in her passport  one that would let her return to the United States if she visited her family.

Image Isaac R. Baichu, 46, an adjudicator for the United States Citizenship and Immigration Services, was arrested after he met with a green card applicant at the Flagship Restaurant, a diner in Queens. He is charged with coercing oral sex from her. Credit... Uli Seit for The New York Times

She came to the United States on a tourist visa in 2004 and overstayed. When she married an American citizen a year ago, the law allowed her to apply to “adjust” her illegal status. But unless her green card application was approved, she could not visit her parents or her brothers’ graves and then legally re-enter the United States. And if her application was denied, she would face deportation.

She had another reason to be fearful, and not only for herself. About 15 months ago, she said, an acquaintance hired her and two female relatives in New York to carry $12,000 in cash to the bank. The three women, all living in the country illegally, were arrested on the street by customs officers apparently acting on a tip in a money-laundering investigation. After determining that the women had no useful information, the officers released them.

But the closed investigation file had showed up in the computer when she applied for a green card, Mr. Baichu told her in December; until he obtained the file and dealt with it, her application would not be approved. If she defied him, she feared, he could summon immigration enforcement agents to take her relatives to detention.