TUCSON, Ariz. - A federal judge ruled Jared Lee Loughner mentally incompetent to stand trial in the Jan. 8 shooting rampage that gravely wounded Rep. Gabrielle Giffords (D., Ariz.), after two medical experts agreed he suffers from schizophrenia and for years has been troubled by delusions and hallucinations.

Judge Larry A. Burns sent Loughner back to the federal medical center for prisoners in Springfield, Mo., for treatment and further evaluation, stopping for now any attempt to try him for the shootings that killed six and wounded the congresswoman and 12 others at one of her neighborhood meetings.

Among those killed was Christina Taylor Green, 9, granddaughter of former Phillies manager Dallas Green. Giffords, 40, is recovering at a rehabilitation hospital in Texas.

Without any change in his condition, Loughner could spend the rest of his life in federal mental-health facilities. But if he shows some signs of improvement, his case could go forward.

Two psychiatric examiners made it clear in their reports that any improvement may be far away, if possible at all. They provided the court with 18 hours of videotape in which they attempted to interview him, much of it with Loughner lying in bed, covers up near his head, answering them with nonsensical statements and often rambling obsessively about treason.

"The defendant is not masquerading," Burns said. "I'm convinced of that today."

The ruling came after U.S. marshals removed Loughner from the courtroom Wednesday when he suddenly started screaming. His father, Randy Loughner, sat in the second row next to Loughner's mother and cried almost the entire time.

Court staff variously reported him saying, "Thank you for the free kill" or "free shot," and then, "She died in front of me." A government source said Loughner was convinced he killed Giffords.

When asked later if he could behave in court, Loughner told Burns that he would prefer to watch the proceedings on a closed-circuit television screen in a courtroom anteroom, where he remained for the rest of the hearing.

Unlike the widely published mug-shot image of the 22-year-old man with wild eyes and bald head, on Wednesday Loughner appeared in court with a heavy and disheveled mop of dark-brown hair, long sideburns, and a wisp of a goatee.

His appearance and outburst only reinforced the findings by the two mental-health experts that Loughner not only did not understand the proceedings and the legal system but also was in no condition to assist in his defense.

"His mental illness at this point is a significant barrier," Burns concluded.

Christina Pietz, a staff psychologist at the Springfield prison, wrote a 52-page report for the prosecution after seeing him daily for a month and interviewing him over 12 hours. She said that he suffers from "major medical illness, schizophrenia," and that he also has "delusions."

She said he did not understand the role of a judge or a jury and harbored an "irrational mistrust" of the process.

Matthew Carroll, a forensic psychiatrist in San Diego retained by the judge, submitted a 43-page report after interviewing Loughner for seven hours. He found him a "schizophrenic, paranoid type," and added that for the "last two or three years, he has had a history of suffering from mental illness."

Carroll agreed Loughner did not have a grasp of how the court process worked, and yet feared he "can't get a fair trial due a conspiracy."

The ruling does not mean Loughner has been declared insane.

"A lot of people are confusing this with the insanity defense," said Praveen Kambam, a forensic psychiatrist at the University of California, Los Angeles. "Being incompetent to stand trial is a fairness thing," he said. "You're making sure your constitutional rights are protected."