Forty-eight students have been dismissed from the University of Virginia after a massive plagiarism investigation that challenged the school's cherished, 160-year-old honor code.

Three of those expelled under the school's student-run disciplinary system already had graduated, so their degrees were revoked, said Christopher Smith, chairman of the committee that oversees the court-like system that addresses accusations of lying, cheating and stealing. Expulsion is the sole penalty available under the code.

Nineteen months after the scandal broke when a physics professor designed a computer program to seek matching passages in 1,500 term papers, the last plagiarism investigation concluded Saturday, Smith said yesterday.

Of 158 students initially suspected by the professor of copying material for their papers in Physics 105, a popular class known as "How Things Work," 59 were charged with violating the honor code. Twenty were found guilty after student-run trials, and 28 others chose to leave the university while "admitting guilt." The others were found not guilty, or their cases were dismissed.

The highly publicized probe generated a wave of concern about cheating in higher education after physics Professor Louis Bloomfield, acting on a tip from a student, wrote a computer program that searched for repeated word patterns in term papers that had been submitted over five semesters in his introductory physics course. Concern about plagiarism has grown with the development of the Internet.

However, Smith said the probe showed that the vast majority of students don't copy. The 48 students found to have violated the honor code represented about 2 percent of the students enrolled in Bloomfield's class during the period in question.

"Our honor system isn't perfect," Smith said. "But I think one thing this really did show is the system is working."

The university's student-run honor system is extremely methodical. After an accusation of cheating, lying or stealing, two students investigate each student's case and file a written report with a three-person panel. Acting as a grand jury, that panel decides whether to charge the student.

For a student to be convicted, it must be proved that the student cheated with dishonest intent and that the act was serious, Smith said. Students charged either can leave admitting guilt or can request a trial before a student jury. In the Bloomfield cases, a few students were tried together, but most had individual trials. The trials can last eight hours and are held only on weekends.

Bloomfield's allegations pushed the honor system to its limits. In an average year, the Honor Committee handles 60 to 80 cases from all parts of the 18,000-student university.

Smith said the expulsions are intended to reflect the university's respect for tradition and honesty -- and the compact between the school and students who agree to the honor system when they arrive.

"We don't wish this to be a stigma placed on students, and we wish them all success possible in their lives," he said. "In fact, our vice president helps them transfer to another institution."