Across the U.S., reform-minded prosecutors have faced pushback from police departments. In St. Louis, issues around police accountability and racial bias were thrown in sharp relief after Michael Brown, Jr. was shot and killed by a Ferguson police officer in 2014. ProPublica reporter Jeremy Kohler is co-writer of the new piece, “A Detective Sabotaged His Own Cases Because He Didn’t Like the Prosecutor. The Police Department Did Nothing to Stop Him.” Kohler talks about that story, which focuses on local figures whose conflict reflects what’s happening in other parts of the country.