Note: Correction appended.

A military psychologist’s unprecedented refusal to testify in a Guantanamo courtroom yesterday will add to a debate that is expected to rage at this weekend’s annual convention of the American Psychological Association.

The professional organization is riven over whether to prohibit members who are in the military or who work with intelligence agencies from participating in the interrogation of suspected terrorists. That issue has prompted the first referendum in the organization’s history this month, for which voting remains open.

The issue has also spurred a New York psychoanalyst, Steven Reisner, to run for president of the APA on a platform of banning psychologists from involvement in national security interrogations “at sites where the conditions violate international law,” he told The New York Sun yesterday.

The APA has long had a close relationship with the military, which is one of the country’s largest employers of psychologists. In recent years, the APA has generally encouraged “engagement” — or involvement in national security interrogations — for the purpose of stopping “interrogations that cross the bounds of ethical propriety,” as the director of the APA’s ethics office, Stephen Behnke, wrote in a letter earlier this year. APA officials also have encouraged involvement in interrogations by psychologists on the grounds that psychologists should assist in the country’s anti-terrorism efforts.

After the American Psychiatric Association voted in 2006 not to allow psychiatrists to be part of the military’s behavioral science consultation teams, which are called “biscuit teams” and advise interrogators, the military began staffing the teams with psychologists alone.

The event that occurred in a courtroom yesterday at the naval base in Guantanamo Bay, Cuba, is expected to add a new dimension to the debate among psychologists this weekend. A lawyer told the court that a military psychologist, who had been asked to testify about the treatment of a detainee, would be invoking her right under the Fifth Amendment privilege to not self-incriminate, the detainee’s lawyer, Major David Frakt, said in a press release sent by an intermediary. The psychologist’s name is protected by court order.

It is the first time a military psychologist belonging to a biscuit team is publicly known to have been asked to give testimony in a Guantanamo court proceeding. The woman’s response suggests that military psychologists are concerned about either their professional licenses or criminal liability.

Court papers filed on behalf of the detainee, Mohammad Jawad, say the psychologist had, in 2003, advised an interrogator to put Mr. Jawad in isolation in an effort to facilitate interrogation, a person familiar with the detainee’s case and who has seen the unclassified legal papers said. The interrogator had sought out the psychologist’s advice because of a concern that Mr. Jawad’s mental state was deteriorating, the person said, adding that Mr. Jawad had been observed speaking to posters on his wall. The psychologist apparently rejected that layman’s diagnosis and believed Mr. Jawad was faking and recommended isolation, the person said.

Nine weeks after Mr. Jawad was removed from a month of isolation, he tried unsuccessfully to commit suicide by either hanging himself or repeatedly banging his head, the source said.

“What is so disturbing about the Jawad case,” the source said, is that the psychologist “is calibrating the level of harm.”

Major Frakt said in the statement that the psychologist’s refusal to testify shows that she “now apparently recognizes that her conduct was criminal in nature.”

Mr. Jawad, now about 24, is accused of throwing an grenade at American forces in Afghanistan while in his late teens.

The effect, if any, of a move by the APA to forbid its members from participating in interrogations is uncertain. While the APA has no control over the licensing of psychologists, which is done by the states, the ABA can censure members on ethics charges. State licensing bodies could consider the APA’s findings in deciding license applications.

Mr. Reisner, the New York candidate for APA president, said he supports extending the APA’s current four- to five-year statute of limitations on ethics complaints in order to investigate the role psychologists have played in national security interrogations.