BOSTON, Dec. 28 -- A federal investigator testified today that Richard C. Reid's sneakers, which he is suspected of trying to ignite on a trans-Atlantic jetliner last Saturday, were a "homemade bomb" containing a highly unstable explosive powerful enough to have blown a hole in the plane.
The explosive, triacetone triperoxide, or TATP, is used almost exclusively by terrorists and favored by Palestinian bomb makers, experts say. But it is so volatile that several bomb makers have been killed by accidental explosions of their own creations.
Another federal law enforcement officer, speaking on condition of anonymity, said today that Mr. Reid's black suede high-top basketball sneakers also contained PETN, a chemical ingredient in plastic explosives. The official said the TATP was designed to be used as an accelerant to ignite the PETN.
PETN, somewhat more powerful than TNT, is commonly used in missiles and bombs, but usually as the detonator, not as the main explosive. PETN is commercially available for uses like detonation cords for setting off mine blasts or building demolitions. It has also been used as a heart medicine, like nitroglycerin, to widen blood vessels.
TATP, by contrast, has "no practical commercial use," said Dr. Jay A. Young, an independent consultant for chemical health and safety in Silver Spring, Md. TATP is extremely unstable and can sometimes be set off just by dropping it.
"Anyone with that in his shoe would have to be very careful not to stamp his shoe in disgust," Dr. Young said.
TATP has become the explosive of choice for Palestinian bomb makers because it is inexpensive and can be made from acetone, hydrogen peroxide and other readily available chemicals. "Something an undergraduate student in chemistry could do with the right training and equipment," said Dr. Jose Almirall, a professor of chemistry at Florida International University in Miami.
In a detention hearing for Mr. Reid in federal court here today, Margaret G. Cronin, a special agent for the Federal Bureau of Investigation, testified that preliminary tests indicated that "the sneakers are a functioning improvised explosive device — in layman's terms, a homemade bomb."
Later Ms. Cronin said, "If he was sitting in a window seat, and the sneakers would have exploded, that would have created a hole in the fuselage." Mr. Reid was in a window seat in Row 29 of the plane, American Airlines Flight 63, which was carrying 197 people from Paris to Miami.
The plane was diverted to Boston after Mr. Reid was seen trying to light a fuse in his shoe and was subdued by crew members and passengers.
Mr. Reid appeared in court today alongside two federal public defenders, one of whom questioned Ms. Cronin for nearly an hour. Throughout the proceedings, Mr. Reid sat quietly, his lanky frame slouching and his head, with its messy mane of dark hair, slightly bowed.
Security was especially tight for the hearing, with everyone entering the courtroom required to remove shoes for screening.
When Mr. Reid entered the courtroom, a woman in the audience shouted: "There he is! Welcome to Boston!" She clapped until federal marshals stared her into silence. Magistrate Judge Judith G. Dein rejected the request of Mr. Reid's lawyers that his handcuffs and leg shackles be removed.
Magistrate Dein ruled that Mr. Reid, 28, was a danger to the community and might flee, and ordered him held without bail.
"He acted with callous disregard for the safety of others," the judge wrote, "and, in fact, appears to have intended to cause them all serious harm, if not death."
Mr. Reid is charged with interfering with the duties of a flight attendant by assault or intimidation, a crime that carries a sentence of up to 20 years. Prosecutors appeared in no hurry today to charge him with possession of explosives or any other more serious charge, although they suggested again that additional charges might be filed at some point.
Asked if prosecutors were delaying additional charges because that would mean more details about Mr. Reid and the accusations against him would become public, Michael J. Sullivan, the United States attorney in Boston, smiled and said, "I think you've put the pieces of the puzzle together."
Mr. Sullivan said today that federal officials were still investigating whether Mr. Reid was part of a conspiracy. Some explosives experts and government officials have suggested that it seemed quite unlikely that Mr. Reid could have acted alone.
But Mr. Sullivan did say that investigators have "no evidence to suggest that he had any accomplice on the flight," either the first flight that Mr. Reid tried to board in Paris on Dec. 21 or the flight on Saturday.
More details emerged about Mr. Reid today, painting a portrait of a man with estranged relationships and a history of getting into trouble and drifting with no job or money.
Magistrate Dein, in her order, said that according to Interpol, Mr. Reid had 16 criminal convictions, 13 for theft, 2 for "offenses against property" and 1 for "offenses against persons." He served some time in prison, but it was not clear when or for how long.
The judge's order said Mr. Reid was also known as Abdul Raheem and was born on Aug. 12, 1973, in Farnborough, England.
"He has no permanent residence and reported that he was most recently living in Paris, France, in different hotels," the order said. "The defendant claims to have resided in Europe all his life in different locations for short periods of time. He is single and has no children. The defendant states that he was never `officially' employed, although he has worked as a construction worker and kitchen helper for different restaurants and construction companies in Europe for brief periods."
The order also said that Mr. Reid has a half brother in England, where Mr. Reid's mother and father live. His parents are divorced. The order said Mr. Reid "has not had any contact" with his father for years.
The judge wrote that Mr. Reid "reports having no assets and no liabilities." He "is not under a doctor's care and is not taking any medication. He has never been treated by a psychiatrist."
In court today, Colin Owyang, the assistant United States attorney who was arguing for Mr. Reid to be held without bail, said Mr. Reid had not tried to enter the United States before, at least not legally, and was "not known to have any close contacts or relatives or friends with which he has kept up a relationship in the United States."
Mr. Sullivan said later at a news conference that Mr. Reid "has no roots in this community." He added, "Based on information that's been gathered today, he has no roots in any community in the world."
Tamar R. Birckhead, one of Mr. Reid's public defenders, led Ms. Cronin, the F.B.I. agent, through a step- by-step description of Mr. Reid's behavior on Flight 63 and his struggle with passengers and crew members.
Ms. Cronin said that after the plane landed in Boston, the captain gave the F.B.I. some items Mr. Reid had been carrying, including a box of matches and some matches that were apparently loose. She said Mr. Reid was taken off the plane, searched, taken to a state police holding cell and read his rights.
Ms. Cronin said he was examined by an emergency medical technician, who told her "the lower number of his blood pressure was a little high." Mr. Reid asked her for water. He was then questioned for about two hours by two F.B.I. agents and a State Department official, she said.
Ms. Birckhead asked if, after the questioning, Mr. Reid appeared tired, and Ms. Cronin said he did. She said his behavior was "compliant."