FORT MEADE, Md. — An Army doctor who disobeyed orders to deploy to Afghanistan because he questioned President Barack Obama’s eligibility for office pleaded guilty Tuesday to one of two charges against him.

Lt. Col. Terrence Lakin of Greeley, Colo., pleaded guilty in a military court to a charge that included not meeting with a superior when ordered to do so and not reporting to duty at Fort Campbell in Kentucky. Lakin, a 17-year veteran, faces up to 18 months in prison and dismissal from the Army when he is sentenced on that charge.

He pleaded not guilty to a second charge of missing a flight he was required to be on, and the court-martial proceeding continued on that count.

A military jury will decide Lakin’s eventual sentence, but Lakin won’t be able to raise the topic he wanted to as part of his original defense: whether Obama was born in the U.S. and therefore can serve as commander in chief. In September, a military judge ruled that whether Obama is qualified under the U.S. Constitution to hold office is not legally relevant in Lakin’s case.

In videos posted on YouTube, Lakin aligned himself with so-called "birthers" who question whether Obama is a natural-born citizen as the Constitution requires for presidents. Lakin, a flight surgeon, says in the videos that any reasonable person looking at available evidence would have questions about Obama’s eligibility to be president and that he had "no choice" but to disobey orders. He said he would "gladly deploy" if Obama’s original birth certificate were released and proved authentic.

Officials in Hawaii say they have seen and verified Obama’s original 1961 birth certificate, which is on record with that state. But birthers have not been satisfied with that assurance or the "Certification of Live Birth" Obama has released. The certification is a digital document that is a record of a person’s birth in the state, but the certificate does not list the name of the hospital where Obama’s mother gave birth or the physician who delivered him.

On Tuesday, members of the military jury that was asked to hear the case were questioned about whether they had heard of the birther movement and what feelings they had about individuals who identify with it. Several said they had heard the term, and all but one said they had at least heard of the case of a military doctor refusing to deploy because of questions about the president’s eligibility for office.

Lakin had been ordered to deploy for what would have been a second tour of duty in Afghanistan.

His parents and two brothers were in court Tuesday, as were supporters who audibly scoffed when one potential juror said he believed evidence that Obama was eligible to be president.

During the morning portion of the trial, Lakin said he had gone to a chapel and done some soul-searching about whether to disobey orders.

"I believe there is a valid question that needs to be asked and answered," he said, referring to Obama’s eligibility to be president.