Over a yearlong period, the AP collected and analyzed decertification records nationwide from 2009 through 2014. Of the nearly 9,000 cases in which officers were decertified, about 1,000 officers lost their licenses for conduct that the AP found included sexual assault, sex crimes such as possessing child pornography and misconduct that ranged from propositioning citizens to consensual but prohibited on-duty intercourse.

The AP compared the cases to a federal government standard to determine whether the officers’ actions amounted to sexual assault or involved other forms of sexual misconduct. The U.S. Justice Department defines sexual assault as “any type of sexual contact or behavior that occurs without the explicit consent of the recipient,” including forced sexual intercourse or sodomy, child molestation, incest, fondling and attempted rape.

While the AP’s review is the most comprehensive available — 41 states provided decertification information — the number is an undercount. Some states did not provide information, and even among states that did, some reported no officers removed for sexual misdeeds even though cases were identified via official records and news stories.

Six states, including some with the nation’s largest law enforcement agencies, said they did not decertify officers for misconduct and kept no official tally of officer wrongdoing. They are California, Hawaii, Massachusetts, New Jersey, New York and Rhode Island. Three states — Louisiana, Maryland and North Carolina — did not provide information to the AP. The District of Columbia said it had no process for certification.

Standards for revoking an officer’s license varied: Almost every state in the U.S. can decertify an officer convicted of a felony. More than 30 have the ability to also decertify for misconduct that may not be criminal. But some states have no reporting requirements, leaving it to local law enforcement to seek the removal of an officer’s license or instead let him or her quietly leave the force.

The quality of information in the decertification records also varied widely.

Florida provided the most detailed review, sharing copies of its statewide database of officers’ employment histories and discipline reports. Georgia supplied spreadsheets with the names and offenses of officers disciplined for misconduct and access to an online database of information. About 20 states provided a list of all decertified officers’ names, agencies and dates and reasons for decertification.

Minnesota refused to name the officers it decertified, though it provided their agencies and reason for decertification. Oklahoma refused to let the AP review all of its files, and released records only for officers it said were decertified for sexual misconduct.

In determining whether an officer had committed sexual misconduct, the AP mostly relied on what a state gave as its reason for decertification. But a cause for decertification was not always clearly stated in the records. Some states gave vague reasons, such as “conduct unbecoming an officer” or “voluntary surrender,” for officers who the AP later found — through additional state information, court or other official records, or media accounts — had actions that met the federal definition of sexual assault or constituted another sex crime or sexual misconduct.

Not all decertified officers face charges or a trial, where the standard of proof is “beyond a reasonable doubt.” State commissions generally apply a “preponderance of the evidence” standard in deciding whether to revoke a law enforcement license.

The AP found fewer than a dozen cases among the sex-related decertifications it studied in which an officer was acquitted in court or later on appeal. Those officers’ licenses were not reinstated, and the cases were included in AP’s count. It is also possible for officers to appeal their decertifications and later regain their licenses.