Stung by an outbreak of violence, including eight killings last weekend alone, police are taking the unusual step of establishing vehicle checkpoints in a crime-ridden neighborhood in the nation's capital.

Starting Saturday night, officers will check drivers' ID and turn away any who don't have a "legitimate purpose" in the area _ a plan that has drawn swift criticism from civil liberties groups.

"The Constitution and the Bill of Rights should not become the next victim of the street violence," said Johnny Barnes, executive director of the American Civil Liberties Union for the National Capital Area. "This plan will treat every resident of that area the way criminals are treated."

The checkpoints come as police try to combat a spike in the number of homicides, which rose 7 percent in the city in 2007 after several years of decline.

Most of last weekend's slayings occurred in the 5th Police District in the city's northeast section, where authorities plan to set up the checkpoints. Already this year, the police district has had 22 killings _ one more than in all of 2007.

"The reality is, this is a neighborhood that has been the scene of many violent crimes, and something had to be done," D.C. police spokeswoman Traci Hughes said.

But the initiative has raised the ire of the ACLU, which plans to watch what happens with the checkpoints before deciding on any legal action.

Officers will stop motorists traveling through the main thoroughfare of Trinidad _ a neighborhood of mostly tidy two-story brick rowhouses that includes Gallaudet University and is near the National Arboretum.

Police will ask motorists to show proof that they live in the area. If they do not have proof, drivers must explain whether they have a reason to be in the neighborhood, such as a doctor's appointment or a church visit.

Police will only search cars if they observe the presence of guns or drugs, officials said. Anyone who does not cooperate will be arrested.

The checkpoints will be enforced at random hours for at least five days, though they could be extended to 10 days, police said. Pedestrians will not be subject to the checkpoints.

District of Columbia Council member Harry Thomas Jr., who represents Trinidad, worried about a potential backlash from angry residents, many of whom question whether the checkpoints will reduce violence.

"Do you want to go home every day and prove that you live at your house?" he asked.

Still, Thomas said, he is taking a wait-and-see approach, noting that many of the recent shootings involved people who drove into the area to buy drugs or settle scores with residents. The checkpoints should make it more difficult for outsiders to come in, he said.

On Thursday, city officials downplayed the significance of the initiative, noting that police have used various checkpoints in the past.

"It's not unlike a sobriety checkpoint or a traffic-safety checkpoint," Hughes said. "This time, it's to make sure violent crime is deterred as much as possible."

Responding to the threat of a legal challenge, interim D.C. Attorney General Peter Nickles cited a similar case involving New York City police, who once stopped motorists in the Bronx at random hours, mostly in the evening, to curtail drive-by shootings, drugs and robberies. Neighborhood residents and commercial vehicles were allowed to pass, while others were turned away.

A federal appeals court ruled in 1996 that those police tactics were constitutional, saying that the checkpoints "were reasonably viewed as an effective mechanism" to reduce drive-by shootings.

In a Supreme Court case from 2000, however, justices struck down random roadblocks used in Indianapolis to screen people for illegal drugs, ruling that they were an unreasonable invasion of privacy. The high court's majority concluded that law enforcement alone is not a good enough reason to stop innocent motorists.

But Nickles said the city had "gone the extra mile" to make sure the roadblocks pass constitutional muster and that officials had tried all other reasonable means to stop the killings, including flooding the area with police officers.

The neighborhood checkpoints aren't the first time Police Chief Cathy Lanier has drawn criticism for measures aimed at reducing crime.

This spring, D.C. police scaled back an amnesty program in which they planned to go door-to-door asking for permission to search homes for guns. Critics complained that some residents could feel intimidated by officers asking to enter their homes. Police later decided to offer the program by appointment only at residents' request.

Neighbors had mixed feelings about the plan for vehicle checkpoints.

"It's needed and it's not needed," said Matthew Simmons, 79, as he sat on the porch outside his rowhouse. Simmons said the checkpoints wouldn't necessarily deter crime. He said a better solution would be to have more consistent police patrols.

Thalia Wiggins, who heard the gunshots across the street related to some of the recent slayings, said the checkpoints are better than nothing. But she was concerned about residents' rights and giving the neighborhood a military feel.

"In the long run, there's no one way to alleviate this problem," she said.

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Associated Press Writer Matthew Barakat contributed to this story.