He was a mild-mannered physicist with a specialty analyzing dental fillings, toiling anonymously at the National Bureau of Standards. (It's now the National Institute of Standards and Technology.) But Wilmer Souder led a double life of sorts and would be unmasked decades later as "Detective X," one of the sleuths who helped crack the "crime of the century"—the Lindbergh baby kidnapping case 85 years ago. "Why in the world would someone like him be involved in the Lindbergh case?" NIST curator Kristen Frederick-Frost wondered, per National Geographic. It was that question that fueled her search for answers, after stumbling on a dusty trove of Souder's notebooks. They helped reveal the physicist, who died in 1974, as a pioneer of early forensic science. A top expert in handwriting, typewriting, and ballistics analysis, Souder helped put away scores of murderers, gangsters, bootleggers, and thieves, per NIST.
Fearing reprisals against his family, Souder kept his role low-key, and there is no accounting of how many high-profile crimes were among the more than 800 cases he worked on. But in May 1932, New Jersey state police asked Souder to examine ransom notes in the Lindbergh kidnapping, which he dubbed the "Adamson case" in his files to throw people off the trail; he eventually testified in the trial that saw Bruno Hauptmann convicted. Joined by NIST scientist John Butler, Frederick-Frost went hunting for more on "Adamson" and came up short until they opened a box in the National Archives marked "Baby Lindbergh Kidnapping Case." "We were ecstatic," she says. There are no detailed case notes to reveal exactly how Souder conducted his analysis. "But in terms of his scientific approach, he was way ahead of his time," Butler says. (Professor claims to have solved the mystery of the Man in the Iron Mask.)