"Joe would never, ever cut corners to put someone in jail or just to sell the case," said the former city investigator, who, noting the sensitivity of the issue, spoke on the condition that he not be named. "I don't care what degrees he did or didn't have. He knew his stuff. ... They aren't going to be able to discredit anything."

Another former colleague, Kenneth Ward, said that Kopera was highly regarded at the state police and was often called on by other investigators with questions about ballistic evidence or bullet trajectories.

"There was never any question about his ability or commitment to his profession," said Ward, who retired as an investigator five years ago and still works as an independent contractor. "The world of ballistics is much more than a bachelor's degree - a large part of it is hands-on, on-the-job training. That's really where Joe learned his craft. I had every confidence in what he told me."

Kopera worked for 21 years in the Baltimore Police Department's crime laboratory before he was lured away in 1991 to join the state police. He was promoted nine years later to supervisor of the firearms and toolmarks unit and also supervised the Integrated Ballistics Identification System.

A favorite witness of prosecutors, Kopera had an authoritative but engaging command of the material he was called upon to describe for jurors, lawyers said. He once walked around a Howard County courtroom, pumping a menacing-looking shotgun used in the fatal shooting of a Marine corporal, explaining the path of the bullets to the jury.

Nethercott, the chief attorney with the state public defender's Innocence Project, said she became concerned about Kopera's qualifications while reviewing transcripts of his testimony in various cases.

On one occasion, she said, he testified that he had a degree from the Rochester Institute of Technology in photo science. On another, he characterized a degree from RIT as being in aerospace engineering. And at other times, he claimed to have a mechanical engineering degree from the University of Maryland.

When representatives of both institutions said they had no record of his having attended either college, defense attorneys asked Kopera for some explanation.

After initially claiming "it was a long time ago," Kopera conceded that he never attended the Rochester Institute of Technology but gave the lawyers a "certificate of training" from the U.S. Air Force that he said the Army certified as the equivalent of a bachelor's degree, Nethercott said.

"We don't know whether it's legitimate," she said.

More troubling was a document that he said was a transcript from his studies at the University of Maryland - a document that Nethercott said was a forgery.

Among the cases that Nethercott and her team are reviewing are the murder convictions of former Baltimore City police Sgt. James A. Kulbicki, whose trial included testimony from Kopera.

Hutchins, the state police colonel, said they have confirmed that Kopera did not earn degrees from either the Rochester Institute of Technology or the University of Maryland.

He said Kopera had completed one year of college of the University of Baltimore. He added that when Kopera applied for a job with the state police, the only educational requirement was a high school degree. "It's a significant concern to me," Hutchins said of Kopera's false claims of college degrees. "Most important to me, as the head of the state police, is to ensure the continuation of operations and to ensure the confidence of the people of the state and the people who use the crime lab."

Although some police departments - including those in Baltimore County and Baltimore City - have their own crime labs, many jurisdictions rely on the state police to process and analyze their evidence.

Hutchins said he has launched an internal audit to review and validate the qualifications of all employees performing forensic science functions at the lab.

He also said he intends to ask the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives to review all pending violent crime cases on which Kopera worked.

Baltimore County State's Attorney Scott D. Shellenberger said a quick review of the office's files revealed fewer than 30 cases - most more than 20 years old - that included analysis or testimony from Kopera.

"Joe was an eminently qualified expert. Whatever the investigation turns up concerning his resume, we believe he built his expertise well after that happened," the veteran prosecutor said. "That being said ... we intend to look at cases in which he was involved, make sure everyone is notified on the defense side and see what, if anything, they want to do."

Maryland U.S. Attorney Rod J. Rosenstein said last night that he, too, has ordered an immediate review of all criminal cases in which Kopera may have played a role for federal prosecutors.

"We have an obligation to disclose and investigate any and all misrepresentations," Rosenstein said. But the federal prosecutor added that a question about Kopera's testimony in a case would not necessarily be enough to overturn a conviction. It was not immediately clear, he said, how many federal prosecutions involved Kopera.

Margaret T. Burns, a spokeswoman for the city State's Attorney's Office, said the office was not planning to review cases in which Kopera provided testimony while he worked for Baltimore police, and that issues arising from individual convictions challenged by defense attorneys would be handled on a case-by-case basis.

Matt Jablow, a Baltimore police spokesman, said that a review of Kopera's personnel file contained a reference that he had a degree from the University of Maryland, which police now know was fictitious. A separate employee file on Kopera, in the department's firearms examination unit, did not contain any references to a degree from the university.

Jablow, the Baltimore police spokesman, said the department does not plan to review Kopera's cases.

"As far as I'm aware, while he was with the Baltimore Police Department, his competence as a firearms examiner was never challenged," Jablow said. He added that the department's firearms examination unit for years has had a policy of having two examiners review each case, and that the city police have their own crime lab.

Sun reporters Matthew Dolan, Justin Fenton, Arin Gencer, Laura McCandlish, Julie Scharper, Gus G. Sentementes, Nick Shields, Andrea F. Siegel and Tyrone Richardson contributed to this article.