Ms. Silsby said Patrick's case qualified for federal jurisdiction because ''this was a crime of violence -- arson is a crime of violence.'' It also qualified because the local prosecutor had decided to turn the case over to her, she said, and ''there was substantial federal interest,'' both because the boatyard was engaged in interstate commerce and because of the seriousness of the crime.

But Prof. Barry Feld, an expert on juvenile law at the University of Minnesota Law School, said that arson by itself did not make a juvenile crime a federal crime, not even a major fire with millions of dollars in damage. ''Kids burn down expensive houses all the time and they don't get charged in federal court,'' Professor Feld said.

Under a federal law dating to the 1970's, juveniles are to be tried in state juvenile court except in special circumstances, said Robert Schwartz, director of the Juvenile Law Center in Philadelphia, a nonprofit law firm that represents juveniles. The attorney general of the United States or the local United States attorney must certify to the court in writing that the case meets these requirements, Mr. Schwartz said.

The first requirement is that there must be ''a substantial federal interest'' in the case, Mr. Schwartz said. In addition, the federal government must also show that the state court refused to take jurisdiction, or that the state did not have available programs for the juvenile or that there was a particularly serious act of violence or the involvement of guns or drugs.

What is particularly puzzling to Patrick's mother, Ms. Collier, his stepfather, Robert Mongue, and his lawyer at the time, Thomas Marjerison, is that they met with Mr. Cantara, the local prosecutor, on Oct. 30, 2002, not long after the arson, and told him that Patrick was prepared to plead guilty in juvenile court.

A few days after the meeting, Mr. Cantara informed the family that he was turning Patrick's case over to the United States attorney.

Statistics suggest how rare Patrick's situation is. In fact, almost all of the 234 juveniles confined in the federal Bureau of Prisons are American Indians, who are considered subject to federal law when they live on a reservation, or young people who committed a crime while on federal land, like a national park or military base, said Dan Dunne, a spokesman for the Bureau of Prisons.