One expert hired by the plaintiffs is expected to testify that only 10 percent of alcohol-related complaints filed against Chicago police officers between 2003 and 2009 resulted in a DUI conviction, court records show. When an arresting officer knew the person they were investigating was a Chicago police officer, it took an average of more than three hours to issue an intoxication test — more than twice as long as if the investigator was unaware of the arrestee's status with CPD, that expert found.