The military has charged a Navy doctor who hosted Naval Academy midshipmen at his home with secretly videotaping the students having sex.

Cmdr. Kevin Ronan is charged with the military equivalent of 18 counts relating to conduct unbecoming an officer and obstruction of justice, as well as violating federal wiretapping law and a Maryland law against making secret recordings, according to a news release from the Navy's Bureau of Medicine and Surgery.

A hearing, similar to a civilian grand jury hearing, is scheduled for Monday at the Washington Navy Yard to determine whether the charges will go forward. They could result in a court-martial, be handled administratively or be dismissed.

Defense attorney William Ferris denied the allegations Tuesday, saying "none of this happened." He said his client is a victim of an extortion attempt by a former student.

"I believe the former midshipman, who was expelled for academic reasons and who wanted Commander Ronan to give him money to complete his education, fabricated this situation in order to extort money from Commander Ronan, and the situation got out of that young man's control," Ferris said.

Ferris said the student asked Ronan for money several times, hoping to find a way to complete his education, get a military commission and avoid having to pay the government back his academy tuition.

Ferris said prosecutors have told him they have a DVD and two videotapes showing students having sex at Ronan's Annapolis home. Ferris, who hasn't seen the recordings, said it's unclear how many midshipmen are shown.

Ferris also said the expelled midshipman had custody of the recordings and showed them to another midshipman, who filed a complaint. Authorities then got the videos from the expelled midshipman, Ferris said. He noted that none of the videos showing midshipmen having sex was found in Ronan's home, office or vehicle.

"The only things that they have are the things that this former midshipman had," Ferris said.

Ferris said he has known about the charges for about a week. The Navy's statement didn't say when Ronan was charged, nor did it identify any of the alleged victims or say how many there were.

"It is important to note that charges are merely accusations and that Commander Ronan is presumed innocent until proven guilty," the Bureau of Medicine and Surgery said in its statement.

If convicted on all charges, Ronan could get up to 18 years in prison, Ferris said.

Ronan was a medical officer at the academy and worked as a doctor for some of its athletic teams. He was transferred to the Navy's Bureau of Medicine and Surgery in May 2006, months before the allegations reportedly happened.

He was also a "sponsor" at the service academy. Sponsors typically are Annapolis residents who open their homes to midshipmen so they can relax on weekends or school holidays. Ronan's participation in the program is suspended pending further investigation, according to an academy spokeswoman. She declined to comment further on the case.