More than 8,000 people have been mistakenly blamed for US immigration violations as a result of the Bush administration's strategy of entering the names of thousands of immigrants in a national crime database meant to help apprehend terrorism suspects, according to a study released last week.
The study, conducted by the Migration Policy Institute, a research group in Washington, relied on statistics released by the Department of Homeland Security that covered 2002 to 2004. The study found that the national crime database was wrong in 42 percent of the cases in which it identified immigrants stopped by the local police as being wanted by domestic security officials.
Many immigration violations, like overstaying a visa, are civil infractions, not criminal offenses typically handled by the police. But since the terrorist attacks of Sept. 11, 2001, domestic security officials have worked to encourage states and localities to help enforce immigration laws by adding the names of thousands of violators - like immigrants evading deportation orders - to the F.B.I. crime database.
The statistics seem likely to fuel the debate over the program, which has been hailed by some as an important tool in the war on terror and criticized by immigration advocates who fear that it will focus attention on ordinary immigrants suspected of violating civil immigration laws, not terrorists.
Michael Gilhooly, a spokesman for the immigration enforcement unit of the Department of Homeland Security, sharply contested the Migration Policy Institute's interpretation of the statistics. He said the results showed that the process was working correctly, allowing local police officers to confirm quickly whether an immigrant is actually wanted by the Department of Homeland Security.
Typically, a police officer investigating a suspect enters the name into the crime database. If the database indicates that the individual is wanted by domestic security officials, the officer is required to confirm that information with a telephone call to immigration officers.
"If it's not the individual we want, the system rules out the individual within 10 minutes," Mr. Gilhooly said.
"The information we're putting into the N.C.I.C. is correct," Mr. Gilhooly said, referring to the F.B.I. crime database, the National Crime Information Center. "The reason individuals are ruled out is because of the accuracy of that information."
Michael Wishnie, a professor of clinical law at New York University and an author of the report, said the statistics raised questions about the accuracy of the immigration data in the database. He said he was particularly concerned that a majority of immigrants affected by the program seemed to be Hispanics who had violated civil immigration laws.