Chicago police officers used stop-and-frisk last summer at more than four times the rate that New York City officers had in the heyday of the practice in 2011, according to a new report by the American Civil Liberties Union in Chicago.



The practice of stop-and-frisk in Chicago disproportionately targeted African American residents, the report found, with blacks making up 72% of pedestrians stopped in the city from May to August of 2014, despite making up only 32% of the city population.



The ACLU report – which was published following new documentation of racially discriminatory policing practices in Ferguson, Missouri, and across the country – was the latest gut check for the Chicago police department. Last week, a senior Chicago police commander in charge of a major unit operating out of the controversial Homan Square police warehouse resigned under pressure.



A spokesman for the Chicago police, Martin Maloney, told the Chicago Tribune that the department prohibits the illegal practice of racial profiling and has taken steps to improve the training of officers on the issue.



In stop-and-frisk incidents, police stop someone ostensibly on suspicion of criminal wrongdoing, and may question the person or pat them down. Critics of the practice, which the US supreme court has ruled to be legal, say it has been abused by police and has led to intimidation and harassment by police officers, especially of minorities.



Cases of stop-and-frisk surged in Chicago with the arrival of police superintendent Garry McCarthy in 2011, ACLU found. McCarthy spent most of his career in New York City, where a policy of widespread stop-and-frisk was pioneered under Mayor Rudy Giuliani in the 1990s.

The practice was closely identified with one of Giuliani’s police commissioners, William Bratton. The current New York mayor, Bill de Blasio, however, won office after campaigning against the practice. De Blasio reappointed Bratton in late 2013, and Bratton has since reined in stop-and-frisk, with 90% fewer cases reported in the De Blasio era compared with January 2012.



Chicago tallied more than 250,000 stops that did not lead to an arrest in the summer of 2014, the ACLU report found. In nearly half of the cases reviewed, police officers “either gave an unlawful reason for the stop or failed to provide enough information to justify the stop”, the report said.

