AUSTIN -- A crime lab scientist for the Department of Public Safety whose shoddy work may have tainted thousands of drug cases had been promoted despite a history of problems doing accurate and timely work, according to a review by the Texas Forensic Science Commission.A commission report adopted Friday found that Houston crime lab worker Jonathan Salvador struggled with chemistry, was told to correct his work in about a third of his cases and, according to his supervisors, routinely scrambled to keep up with monthly work expectations.Salvador was suspended in 2012 after his work at the DPS lab came into question. The Texas Court of Criminal Appeals has overturned more than a dozen convictions as officials grapple with the scope of Salvador's work, which involved nearly 5,000 cases in 36 counties."The fact that this guy went on as long as he did without ever being figured out is appalling," said Jeff Blackburn, an attorney with the Innocence Project of Texas."Once DPS figured it out, they did the right thing, but they should have gotten wise to him long before."Salvador's work came under scrutiny after a co-worker told a supervisor he suspected Salvador used test results from one drug case to support a conclusion in another. Investigators retested 100 other cases and found more errors.In April 2012, the DPS sent an email to prosecutors telling them of the agency's review and attaching a list of affected cases from their jurisdictions. The email also said prosecutors could submit any evidence from these cases for retesting by another lab worker.The forensic commission report found that Salvador's supervisors had noted that about 1 in 3 reports he turned in needed some sort of correction, from simple administrative fixes to more serious ones, including technical problems with his findings. The report noted that other lab workers had a correction rate of less than 10 percent.Evaluations noted that Salvador struggled with an "overall understanding of chemistry, especially in difficult cases," the report said. Supervisors described Salvador's struggles as "very systemic" and his work as "right on the edge" of acceptability.The report also found that Salvador was promoted and given a raise because he was friendly and a hard worker who tried to improve. Supervisors didn't consider the work issues "catastrophic," the report said, but in at least one case, an error included a misplaced decimal point that could have led to a felony charge instead of a misdemeanor possession charge.Salvador's poor work has created major problems for prosecutors who have won convictions in his cases. The appeals court has opened the door for potentially overturning convictions in any Salvador case in which the drug evidence has been destroyed or was left in his sole custody.This year, the Texas District and County Attorneys Association told its members that the cases Salvador handled "may all be jeopardized."The commission stopped short of that threshold, however, noting that in many cases, evidence still exists to be retested."It makes no sense, when the evidence remains ... that those convictions should be overturned," said Commissioner Sarah Kerrigan, chairwoman of the forensic science department at Sam Houston State University, who led the panel's investigation and report.