NASHVILLE, Tenn. — A woman visiting an inmate at a privately run Tennessee prison says guards forced her to expose her genitals to prove she was menstruating when she tried to take a sanitary napkin into the facility, according to a lawsuit filed Thursday.

The woman, identified only as Jane Doe in the lawsuit filed in federal court in Nashville, said she had already cleared one security checkpoint at the prison about 85 miles southwest of Nashville on April 20 when guards noticed a menstrual pad sticking out of her pocket.

The lawsuit says that when the guards told her she would need to prove that she was menstruating, she offered to leave the prison or leave the pad behind. She also offered to show guards her used menstrual pad.

Instead, she says she was instructed to go into a bathroom stall, drop her pants and underwear and allow a female officer to inspect her genitalia.

The lawsuit claims that the woman was not free to leave and that prison visitor policy at the time stated: "Any visitor refusing a search of any type may be permanently restricted from visiting."

Calls and emails to Correction Corporation of America and the Tennessee Department of Correction were not immediately returned.

The woman says she spoke with the head of security at the South Central Correctional Facility in Clifton the following day and was told that such inspections were standard policy there.

It was not immediately clear whether similar inspections are done at other prisons. However, the lawsuit says that Tennessee Department of Correction policy allows strip searches only when reasonable suspicion exists, and that such searches must be approved by a supervisor on a case-by-case basis.

Such a search would be inconsistent with typical practices at prisons, said Martin F. Horn, a former commissioner of correction in New York City and former secretary of corrections in Pennsylvania.

A prison could use a metal detector or X-ray scan, or require a no-contact visit if the pad raised suspicion, said Horn, a distinguished lecturer at the John Jay College of Criminal Justice in New York.

The woman has asked the court to let her proceed anonymously because of the embarrassing details of the claims. The lawsuit seeks damages for the woman's humiliation and asks that the prison's policy on such searches be banned because it's unconstitutional.

"Plaintiff should not be forced to make the intolerable choice between abstaining from visiting an inmate in prison because she is on her period and visiting the prison with the risk of being subjected to another humiliating and degrading search of her exposed genitalia," the lawsuit says.