Still he continued to conduct trials. Karns can’t remember the companies he worked for, but I was able to establish that at least two were run for Cephalon, a pharma company based in Frazer, Pennsylvania, that has annual revenues in the billions. At least one trial involved opioid painkillers that, like Demerol, can be abused. In June 2011, shortly after barring his father from the practice, Adam Karns took over the last of these trials. Teva, the Israeli firm that now owns Cephalon, says: “To the best of our knowledge, Cephalon was not aware at that time that Robert Karns was under investigation for drug abuse.”

By December 2011, it had all become too much. The state medical board reviewed evidence of Karns’s drug use, and suspended his license. But they didn’t stop there. A few weeks later, an undercover operative working for the board visited the new solo practice Karns had established, a few minutes’ drive from his former office. The bogus patient complained of back pain and a cough, and was given prescriptions for both. The board’s account of the sting includes Karns’s immediate response to being caught breaching his suspension: “So I broke the rules … Guilty as charged.” He was later allowed to practice once more, under the supervision of another doctor, but it was only a temporary reprieve. In November 2012, Karns was finally stripped of his California medical license.

Almost to the end, Karns was being sought out for new studies. His final entry in the FDA database, submitted in March 2012, gives the address of his solo practice. Karns says that no clinical trials were actually run there. But evidently he was selected as a clinical investigator, and his paperwork was submitted to the FDA. Even after all the mistakes and the drug abuse and the disciplinary actions, there apparently was still a company somewhere that was prepared to employ Karns to run a clinical trial.

Karns may be an extreme case, but he’s far from alone. My trawl netted dozens of doctors selected to work on clinical trials over the past five years who had previously been censured by state medical boards. Thousands of doctors are hired each year to test experimental drugs, making this a small minority. But most doctors have clean records, so companies should have few problems finding recruits without red flags against their name.

It’s hard to know whether the doctors who were sanctioned caused problems in the clinical trials they ran, because the FDA rarely inspects trial sites. Karns was inspected in 2005, when nothing untoward was found, but there is no record of anyone coming to call during his later descent into drug abuse. (He denies ever putting trial volunteers at risk: “Was there any time I was impaired with a study patient? Absolutely not.”)

Yet there are good reasons for thinking that a doctor who errs once might do so again. A 2007 study found that doctors who were sanctioned by state medical boards in one five-year period were at least 10 times as likely as their peers to get in trouble over the following four years. More important, I came across several doctors who’d got into serious problems in both regular practice and clinical trials—including Michael Berger.

In April 2010, FDA inspectors arrived at Immunovative Therapies’ Carlsbad site. The records held there described a technically demanding study based on a radical idea. The treatment was known as AlloStim, and the idea was to take immune system cells from healthy donors, process the cells in the lab, and then inject them into cancer patients. The hope was that the cells would trigger an immune reaction aimed at the patients’ tumors.

Even enrollment was complex: blood tests and other analyses were used to assess whether patients met the extensive inclusion criteria. Once enrolled, they received three doses of AlloStim, followed by a procedure called tumor cryoablation. Using CT scans as a guide, Berger or a colleague had to pump chilled argon gas through a needle inserted into one of the patient’s tumors. The aim was to freeze the cancerous tissue, prompting it to release a chemical signal that would be targeted by the patient’s immune system. One hour later, another dose of AlloStim was to be injected straight into the tumor, followed a week later by a final dose into a vein.

As the doctor running the trial, Berger was responsible for ensuring that these procedures were followed. He had to oversee the collection of data, including MRI scans of patients’ tumors and tests of immune function, and verify that batches of AlloStim were sterile. These tasks apparently proved beyond him. FDA officials discovered that patients had been given AlloStim by the wrong method, or given numerous doses that they were not supposed to receive. One patient was enrolled despite not meeting the criteria. Some had received batches that were past their expiry date, or that had failed tests for bacterial contamination. Berger and his team had already treated 42 patients in one trial when the FDA visited, but the inspectors were so alarmed that they shut down the second trial he was running for Immunovative Therapies. The agency later told Berger that it would bar him from running clinical trials altogether—a lengthy process that ended with his disqualification in April this year.

The FDA considers the details of trials of experimental drugs to be commercial secrets, and so wouldn’t tell me whether any patients were harmed as a result of Berger’s failings. Michael Har-Noy, Immunovative Therapies’ CEO, declined to comment, and Berger would not be interviewed for this article. (Documents reveal that Berger told the FDA that he notified and monitored the patients who received the batches of AlloStim that failed sterility tests, and that he had not detected any adverse events, but the agency described his response as “unacceptable.”) One investor in the company was prepared to talk, however. Ronald Lachman, a Chicago-based venture capitalist, contends that the FDA’s inspectors overreacted. Lachman’s late wife was one of the trial participants, and he’s convinced that the treatment helped her. “Things that show so much promise are few and far between,” laments Lachman, who put more than $1 million into Immunovative Therapies.