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To test the theory of how the baby was abducted and then killed early on, Schwarzkopf had duplicates constructed of the makeshift ladder used to climb into Charlie's second-story nursery window and the ransom letter, and reenacted the crime himself. The 165-pound Schwarzkopf carried a sandbag weighing the same as Charlie down the ladder, and when he stepped onto the highest rung of the lower portion of the wooden ladder (which, like the real one, consisted of two hinged sections and a third one attached at the crime scene), the side rail split, just like on the real ladder. Schwarzkopf dropped the bag, and it struck the cement windowsill of the library, echoing the massive skull fracture that served as Charlie's cause of death. Schwarzkopf had the written communications in evidence sent to graphologists, who concluded that they were all written by one person, most likely German in origin.[citation needed]

In the late 1932, Schwarzkopf was put in touch with New York psychiatrist Dudley D. Schoenfeld, who concluded from the kidnapper's writings that the perpetrator was a mechanically inclined, 40-year-old German suffering from dementia paralytica, caused by feelings of powerlessness, which is considered an impressive early example of criminal profiling. Schwarzkopf also had pieces of the ladder analyzed by wood technologist Arthur Koehler, who determined from four extra nail holes that rail sixteen of the ladder, unlike the wood used to make the rest of the ladder, had been previously used for some other purpose. It was presumed that was because the kidnapper ran out of lumber and cannibalized whatever wood was on hand for that rail. Koestler concluded on November 19, 1933 that side rails twelve to fifteen came from National Lumber and Millwork Company in the Bronx.[citation needed]

Investigation of bills from the ransom money that turned up in circulation led to the September 19, 1934, arrest of Bruno Hauptmann, a 35-year-old German skilled carpenter who once worked at National Lumber and Millwork, which was ten blocks from Hauptmann's residence. By matching grain patterns and nail holes, Koehler determined that rail sixteen had been removed from Hauptmann's attic, which was missing a floorboard, and featured nail holes in four successive joints, where it would have been hammered down. Hauptmann was tried and convicted for murder and was executed on April 3, 1936.[7]

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But from his personal staff I heard that you would never want to raise his ire.