A U.S. government doctor saw marks on the back of a Virginia student charged in a plot to kill President Bush but could not conclude that the lines came from physical abuse, the doctor testified at a hearing yesterday.

The testimony is significant, because attorneys for Ahmed Omar Abu Ali claim that their client was tortured while in Saudi custody and that a confession that forms the crux of the government's case was coerced.

The four "linear marks" were seen on Abu Ali's upper back as he was flown to Northern Virginia in February to face charges of plotting with al Qaeda to kill Bush, according to the doctor, Richard Schwartz. Schwartz, chairman of emergency medicine at the Medical College of Georgia and an FBI contractor, examined Abu Ali during the flight.

Under cross-examination from defense lawyers, Schwartz acknowledged that the marks could have been a result of whipping. Abu Ali's claim of torture is the subject of a hearing continuing this week in U.S. District Court in Alexandria.

Schwartz also testified that the marks could have come from old scarring or could have been self-inflicted. "It's rather inconclusive what caused them. . . . Based on his history and physical, they did not seem consequential," he said. "I examine many, many patients every day, and I see marks like this on many people. It's one of those things that can occur in life."

Schwartz added that he did not mention the marks in his two-page report -- which was based on his 10- to 15-minute exam -- and did not ask Abu Ali where they came from or tell anyone about them at the time.

The doctor's testimony came on the third day of the hearing, which is examining whether Abu Ali's confession to taking part in the alleged al Qaeda plot was extracted through torture. Prosecutors deny that Abu Ali, 24, was tortured and have presented testimony from FBI agents and State Department officers who saw him in Saudi Arabia and said he never raised the subject with them and seemed healthy.

Two other doctors who examined Abu Ali found evidence that he was tortured in Saudi Arabia and said scars on his back were consistent with his having been whipped, defense attorneys have said in court papers. If a judge accepts the defense arguments, he could throw out much of the government's evidence.

The hearing began last week and is scheduled to last through Thursday. The defense's doctors are scheduled to testify later this week.

Abu Ali is charged with conspiracy to assassinate Bush and other terrorism counts in connection with the alleged plot, which prosecutors say also envisioned a Sept. 11-style attack inside the United States. Prosecutors say that Abu Ali has admitted his participation and that he planned to shoot Bush or blow him up with a car bomb. He admitted that the plan never got past the idea stage, prosecutors have said in court papers.

During the hearing last week, prosecutors introduced a 13-minute videotape in which Abu Ali said he joined the al Qaeda plot while in Saudi Arabia because of his disgust with U.S. support for Israel.

Yesterday, FBI agent Barry Cole testified that when he interrogated Abu Ali in Saudi Arabia in September 2003, the Falls Church man said he had been subjected to "mental torture" but did not mention physical abuse.

FBI agents followed up on the mental torture allegation, but Abu Ali refused to answer, Cole testified. "He just told us to forget about it," Cole said. "[He said] we wouldn't understand, because it was a Muslim thing.''

Ahmed Omar Abu Ali is accused of plotting to kill President Bush.