The American Civil Liberties Union of Wisconsin has filed a federal class-action lawsuit against the City of Milwaukee over what it says is an unconstitutional “stop and frisk” program that targets people of color.

The suit is filed on behalf of six black and Latino plaintiffs who say they were stopped, searched and sometimes detained without cause.

“For the last decade, the Milwaukee Police Department has pursued an aggressive and unconstitutional policing strategy that treats people of color as suspects for no good reason, stopping innocent men, women, and children as they try to go about their daily lives,” said Jason Williamson, senior staff attorney with the ACLU’s Criminal Law Reform Project. “This approach forces tens of thousands to live under suspicion every time they step outside.”

An ACLU statement says Charles Collins, one of the lawsuit’s six plaintiffs, is a Black military veteran who has lived in Milwaukee for 55 years.

“If I’m going out, I’m always looking over my shoulder even though I’ve done nothing wrong,” said Collins, according to the statement.

“The Milwaukee Police Department has prioritized widespread, unconstitutional stop-and-frisk practices over its relationship with communities of color in this city,” said Karyn Rotker, senior staff attorney at the ACLU of Wisconsin. “By routinely stopping thousands of people who have done nothing wrong, the department has undermined its relationship with Milwaukee residents and created a profound lack of trust in those communities—which compromises the department’s ability to investigate crimes.”

The number of traffic and pedestrian stops in Milwaukee rose from 66,657 in 2007 to 196,434 in 2015, according to police department data cited in the lawsuit.

According to data the ACLU obtained from the police department through an open records request, black people made up 72 percent of the more than 33,300 pedestrian stops officers conducted between 2010 and 2012.

The ACLU’s analysis of those stops found that 41 percent lacked a clear explanation, with the reasons either not listed or described as “other,” “suspicious circumstances,” ”suspicious vehicle” or “suspicious person.”

The lawsuit demands that the court order the police department to immediately end the program and to declare that the department is violating the Fourteenth Amendment’s equal protection clause and the Fourth Amendment’s protection against unreasonable searches and seizures.