GUANTÁNAMO BAY, Cuba — A forensic psychiatrist testified on Thursday that, based on documents he reviewed, a Saudi prisoner accused of plotting the suicide bombing of the Navy destroyer Cole voluntarily confessed to having a role in the attack after four years in the C.I.A.’s secret prison network.
The psychiatrist, Dr. Michael Welner, was offering an expert opinion as a government consultant to counter arguments by defense lawyers that the prisoner, Abd al-Rahim al-Nashiri, 58, was conditioned to tell federal agents at Guantánamo Bay what they wanted to hear because he had been waterboarded, humiliated, threatened and kept in isolation for years.
But Dr. Welner said transcripts, prison medical records and guard records showed that Mr. Nashiri was a sometimes belligerent, unafraid and bragging prisoner who displayed free will and chose what topics he wanted to discuss when federal agents questioned him in January and February 2007 at a former C.I.A. facility at Guantánamo Bay called Camp Echo.
In the records, Dr. Welner said, “I saw that he was in fact bold in terms of what he was expressing about himself. He was expressing choices that he was making in the course of that time frame.”
At issue in this instance is whether the judge will allow testimony about the prisoner’s supposed 2007 confessions, as well as a transcript of his status hearing that year, as trial evidence. Defense lawyers want the material excluded as tainted by his torture.
Seventeen American sailors were killed in Al Qaeda’s suicide bombing of the Cole off the coast of Yemen on Oct. 12, 2000. No start date has been set for Mr. Nashiri’s death-penalty trial as lawyers litigate what evidence will be allowed.
Dr. Welner said he did not interview or observe Mr. Nashiri in preparation for his testimony. He was specifically tasked with evaluating the prisoner’s state of mind from his arrival at Guantánamo in September 2006 through March 2007, and testified from a classified setting near Washington, D.C. — while Mr. Nashiri listened from a holding cell behind the court.
Defense lawyers have devoted months of on-again, off-again hearings to testimony about what C.I.A. prison staff members did to Mr. Nashiri beyond waterboarding before he reached Guantánamo.
In his last years in the C.I.A. prison network, they said, threats were no longer required to keep him talking, just the periodic appearance of the two interrogators who in 2002 waterboarded him, John Bruce Jessen and James E. Mitchell. Both were C.I.A. contract psychologists at the time.
Dr. Welner described the techniques used on Mr. Nashiri as more benign. Drs. Mitchell and Jessen used the measures and subsequent visits, Dr. Welner said, to make sure Mr. Nashiri was “cooperative and collaborative” in interrogations and “to ensure a social relationship that was not antagonistic.”
Defense lawyers portray Mr. Nashiri as a torture victim. Dr. Sondra Crosby, a defense consultant who specializes in treating victims of trauma, has testified that Mr. Nashiri has nightmares about drowning and suffers from the aftermath of physical, psychological and sexual trauma.
He gets nauseated and vomits from flashbacks to a period when the C.I.A. confined him nude and shivering inside a chilled, cramped box, and he has gastrointestinal pain from rectal abuse and joint pain from being shackled in painful positions, she has testified.
In 2013, a board of U.S. military mental health experts diagnosed Mr. Nashiri with post-traumatic stress disorder and depression but found him competent enough to stand trial.
But Dr. Welner testified that the 2006-7 Guantánamo records showed no symptoms of PTSD at that time, nor that Mr. Nashiri was in a state of “learned helplessness.” Transcripts and accounts indicated that Mr. Nashiri spoke voluntarily to agents of the F.B.I. and the Naval Criminal Investigative Service, so-called clean teams, because he understood he could also refuse to talk, the doctor said.
Prosecutors provided Dr. Welner with “a very large classification file” to review. It included transcripts of agents’ descriptions of the 2007 interrogations, testimony and notes by a military psychiatrist who was treating the prisoner at the time, prison guards’ notes and Mr. Nashiri’s “account of his unwanted experiences in custody.”
In an apparent reference to a secret surveillance and transcription system used at Guantánamo, Dr. Welner also said he was able to read Mr. Nashiri’s “expressions, how he expressed things, what he was specifically saying at that point of time.”
As an example, he said, records showed that Mr. Nashiri “objected to cell searches.”
“He was spitting and cursing at staff,” Dr. Welner said.
Members of the public watching the proceedings hear the audio on a 40-second delay, time enough for the judge or a security officer to mute the sound if they suspect something classified has been said. In the session on Thursday, court officers switched the audio to white noise just after Dr. Welner said the prisoner was “adamantly expressing himself,” complaining about frequent searches of his prison cell.
When the audio resumed, a prosecutor, Lt. Tess V. Schwartz of the Navy, cautioned the doctor to wait until a closed national security session to discuss “force protection” issues, and then the feed to the public was cut again.