Police officers in the US were charged with more than 400 rapes and over 600 groping offenses during a nine-year period between 2005 and 2013, according to a new academic report.
There was an average of 45 rapes a year by police, according to research from Bowling Green State University in the US state of Ohio.
Forcible fondling was more common, with 636 instances taking place during the nine-year period, the study found.
Yet experts say those statistics are, by no means, comprehensive because data on sexual assaults by police are almost nonexistent.
"It's just not available at all," said Jonathan Blanks, a research associate with the Cato Institute's Project on Criminal Justice. "You can only crowdsource this info."
"The system is rigged to protect police officers from outside accountability," Blanks said. "The worst cops are going to get the most protection."
The researchers compiled their list by documenting cases of sworn nonfederal law enforcement officers who have been arrested. But the 2016 federally funded paper, "Police Integrity Lost: A Study of Law Enforcement Officers Arrested," says the problem isn't limited to sexual assault.
"There are no comprehensive statistics available on problems with police integrity," the report says.
"Police sexual misconduct and cases of police sexual violence are often referred to as hidden offenses, and studies on police sexual misconduct are usually based on small samples or derived from officer surveys that are threatened by a reluctance to reveal these cases," the study added.
The latest numbers, for instance, are the result of Google alerts on 48 search terms entered by the university’s researchers. The scholars then follow each case through adjudication.
One of the greatest obstacles to understanding the extent of police sexual violence is the victims' reluctance to report the crime.
"Who do you call when your rapist or offender is a police officer? What a scary situation that must be," said Philip Stinson, an associate professor of criminal justice at Bowling Green State University.
One statistic from Stinson indicates that for every sexual assault that makes the news, there are almost always more victims -- on average, five more.
About half of the victims are under 18, researchers say.
Many victims include vulnerable people that police officers are supposed to be protecting, according to the report.
"Opportunities for sex-related police crime abound because officers operate in a low visibility environment with very little supervision," it says. "The potential victims of sex-related police crime include criminal suspects but also unaccompanied victims of crime."