A study of female drug offenders in the St. Louis area finds one-quarter report experiencing police sexual misconduct, MedicalXpress reports.

The study, published in the American Journal of Public Health, included 318 women who were supervised by a probation or parole officer for a non-violent offense. The women completed surveys led by trained interviewers, the article notes.

“It’s important that the police force acknowledges that sexual misconduct may exist among the force, so that it can be stopped and eventually prevented,” lead investigator Linda B. Cottler of the University of Florida College of Public Health and Health Professions, said in a news release.

One-quarter of women in the study said they had a lifetime history of police sexual misconduct. Of these women, 96 percent said they had sex with an officer who was on duty, and 24 percent said they had sex with an officer while the officer’s partner or another officer was present.

The study also found 54 percent of the women said the officer offered favors in exchange for sex, such as to avoid arrest, or being charged with a crime; 87 percent said officers kept their promises. About one-third of women who said they experienced police sexual misconduct described the encounter as rape.

An estimated 1.3 million American women were incarcerated or under correctional supervision in 2009, up from 600,000 in 1990, the article notes.