There are plenty of incentives for bad behavior. Finding enough people to test potential treatments can be difficult, notes Hank Greely, a Stanford University law professor who studies ethical and social issues in bioscience. “You’ve got trial runners who are desperate to get subjects,” he says, adding that the sizable fees often paid to doctors and sites create incentives “for fraud or pushing the gray zone.”

Greely notes that even in a big trial, problematic data for a small number of participants can skew results if a drug shows only borderline effectiveness. “If the results come in within a hair’s breadth of [statistical significance] in little subgroups,” he says, “five improperly enrolled subjects could be a big deal.”

Given the possible financial windfalls to trial sites for cheating, pharma companies, CROs, and FDA should exercise more preemptive and forceful oversight, Greely says. “Will you ever know [if trial results are being doctored]? Certainly not if you never look.”