Law enforcement experts and housing researchers argue that rising crime rates follow Section 8 recipients to their new homes, while other experts discount any direct link. But there is little doubt that cultural shock waves have followed the migration. Social and racial tensions between newcomers and their neighbors have increased, forcing suburban communities like Antioch to re-evaluate their civic identities along with their methods of dealing with the new residents.

The foreclosure crisis gnawing away at overbuilt suburbs has accelerated that migration, and the problems. Antioch is one of many suburbs in the midst of a full-blown mortgage meltdown that has seen property owners seeking out low-income renters to fill vacant homes. The most recent Contra Costa County records available show that from 2003 to 2005, the number of Section 8 households in Antioch grew by 50 percent, to about 1,500 from 1,000. Many new residents are African-American; Antioch’s black population has grown to about 20 percent, from 3 percent in 1990.

Federally assisted tenants in Antioch brought a class action lawsuit against the police department last month, claiming racial discrimination, intimidation and illegal property searches. The lawsuit, which was filed in the Northern District of California, claims that the police routinely questioned Section 8 residents about their housing status and wrote letters to the county’s housing authority recommending termination of subsidies. They say the police also threatened Section 8 landlords for infractions by tenants. A December 2007 study of Antioch police records by Public Advocates, a law firm in San Francisco, counted 67 investigations of black households, compared with 59 of white families; black households, it found, are four times as likely to be searched based on noncriminal complaints and to be contacted by the police in the first place.

Chief James Hyde of the Antioch Police Department denied that his officers routinely asked whether tenants were Section 8 recipients and said that the police department did not have information about which homes were on federal assistance. But Chief Hyde also said that the local housing authority was not meeting its obligation to screen tenants properly, and that as his department focused on nuisance issues, the police had become a de facto enforcement arm of the federal government.

Image Darrell Turner of the N.A.A.C.P. talked to a private security guard who had stopped black teenagers on the block. Credit... Eros Hoagland for The New York Times

“Other cities have come asking us for guidance,” Chief Hyde said.

The Section 8 program is designed to encourage low-income tenants to settle in middle-income areas by subsidizing 60 percent of their rent. The United States Department of Housing and Urban Development issued 50,000 more vouchers for suburban relocations in 2007 than in 2005, bringing the total number of renter families to 2.1 million.