In Chapter 9 of Probably Overthinking It I wrote about Drug Recognition Experts (DREs), who are law enforcement officers trained to recognize impaired drivers. I reviewed the research papers that were supposed to evaluate the accuracy of DREs and I summarized my impressions like this: What I found was a collection of studies that are, across the board, deeply flawed. Every one of them features at least one methodological error so blatant it would be embarrassing at a middle school science...