A decade ago the Minnesota Board of Medical Practice accused Dr. Faruk Abuzzahab of a “reckless, if not willful, disregard” for the welfare of 46 patients, 5 of whom died in his care or shortly afterward. The board suspended his license for seven months and restricted it for two years after that.

But Dr. Abuzzahab, a Minneapolis psychiatrist, is still overseeing the testing of drugs on patients and is being paid by pharmaceutical companies for the work. At least a dozen have paid him for research or marketing since he was disciplined.

Medical ethicists have long argued that doctors who give experimental medicines should be chosen with care. Indeed, the drug industry’s own guidelines for clinical trials state, “Investigators are selected based on qualifications, training, research or clinical expertise in relevant fields.” Yet Dr. Abuzzahab is far from the only doctor to have been disciplined or criticized by a medical board but later paid by drug makers.

An analysis of state records by The New York Times found more than 100 such doctors in Minnesota, at least two with criminal fraud convictions. While Minnesota is the only state to make its records publicly available, the problem, experts say, is national.