The District of Columbia’s police department spent tens of thousands of public dollars and countless hours readying itself for a critical outside accreditation — only to pull the plug at the last minute because the department failed to adequately prepare for the review.

Accreditation from the Commission on Accreditation for Law Enforcement Agencies Inc. had been the decades-long goal of police leadership. But when the commission sent staff to inspect the police department in late March — after years of meetings, test runs and policy changes from within the police department — D.C. police officials hadn’t finished paperwork for the test.