Your article about Johnny St. Valentine “Master Jehru” Brown Jr. (“False Witness,” 7/21) is both illuminating and incredibly frightening. Detective Brown apparently engaged in “testilying” for almost two decades without anyone’s ever contesting his credentials or challenging his status despite the numerous suspicions of his colleagues, members of the bar, and, I suspect, not a few judges. What makes his appalling perjurious career even more inexcusable is that even the most cursory background questions would have revealed Brown’s duplicity. Simple preliminary deposition questions such as the address of the pharmacy where he worked, his D.C. professional license number, or a check of his alleged pharmacological board certification (which he claimed existed since 1968, when he was 26 years old) should have been asked. These or any of a number of other questions that most first-year lawyers would ask could have revealed Jehru’s scam. This would have, perhaps, helped exonerate those who are innocent and kept those who are guilty where they belong. Instead, once again, the criminal-justice system of the nation’s capital endures an assault on its competency and, inadvertently, puts another arrow in the quiver of those who would keep home rule a distant target.

There’s a lesson to be learned here, not just for would-be perjurers, but also prosecutors, who relied on his testimony, and defense counsel, who sought to undermine it: Do your homework. Remember the simple stuff. And don’t believe the hype. If someone is going to present himself as an expert in his field, he should withstand at least a cursory review of his credentials. No one should get a bye in this regard, least of all an expert who helps put people away for a very long time.

Alexandria, Va.