After numerous Lindbergh case sideshows and wild-goose-chases, the investigation slowed, then came to a crawl during the first nine months of 1934. Because the ransom negotiations had taken place in the Bronx, and most of the ransom bills were being passed in Manhattan, the focus of the investigation had shifted to New York. On September 14, 1934, a gas station attendant in Manhattan, suspicious of a ten-dollar gold certificate offered by a customer (the country had switched to greenbacks in May, 1933), scrawled the gold note passer's license number on the margin of the bill. A bank employee, after checking the bill's serial number against the widely circulated ransom list, notified the FBI who sent an agent to retrieve the bill. The license number came back to a 1930 Dodge registered to a Richard Hauptmann, a resident of the Bronx who lived a few blocks from where several pieces of the kidnap ladder had been purchased.
The next day, two and a half years after the kidnapping, a team of investigators from the New Jersey State Police, FBI, and New York City Police Department, pulled Hauptmann out of his car as he crossed into Manhattan from the Bronx. Hauptmann was in possession of a twenty-dollar ransom bill, spoke with a German accent, and closely met the description of John Condon's “Cemetery John.”
The next afternoon, Albert S. Osborn began analyzing Hauptmann's handwriting, samples the subject had given to officers who had read to him Osborn's carefully worded paragraph. A few days later the police found, hidden in Hauptmann’s garage, $14,000 of the ransom money. In explaining the loot, Hauptmann came up with the so-called “Fisch Story” involving a business partner named Isadore Fisch who had supposedly left the money with Hauptmann for safekeeping a month before Hauptmann's arrest. Fisch had since returned to Germany where, penniless, he had died of tuberculosis. Investigators broke the “Fisch Story” by interviewing several credible merchants who identified Hauptmann as passing ransom bills months before the money had supposedly come into his possession from Fisch.
About the time Albert S. Osborn reported that Hauptmann was the writer of the ransom documents, police found a gap in Hauptmann's attic floor that had once been filled by a plank used in the construction of the kidnap ladder. This board, referred to as Rail 16, contained holes that lined up to nail punctures in the floor joists, and matched up, grainwise, to the attic plank from which it had been cut.
The police had now connected Hauptmann to the crime through his handwriting, his attic floor, and the ransom money. He matched Condon's description of “Cemetery John,” possessed a serious crime record in Germany, and, as an unemployed carpenter in the height of the Great Depression, had spent $36,000 between the time of the ransom exchange and his arrest. When confronted with this evidence, true to the low-grade sociopath that he was, Hauptmann maintained his innocence. Therefore, to convict him, the prosecution would have to rely on circumstantial evidence, principally the handwriting, and the identification of Rail 16.
Based upon the testimony of Albert S. Osborn and another document examiner, Charles A. Appel, Jr., the head of the FBI's new crime lab, a grand jury in New York indicted Hauptmann for extortion.
Hauptmann's six-week murder trial began on January 2, 1935 in Flemington, New Jersey. The heart of the state's case, the handwriting evidence, consisted of eight forensic document examiners whose testimony lasted four days, producing a transcript of 800 pages. The questioned evidence included:
- The nursery note
- The fourteen extortion letters
- The “Boad Nelly” note
- The address on the mailed sleeping suit package
- John Condon’s phone number written on a board in Hauptmann's closet
The handwriting evidence totaled 1,400 words.
The known, conceded writing consisted of hundreds of words in Hauptmann's notebooks; his car registration signatures; insurance papers and other personal documents. The request samples involved handwriting elicited from Hauptmann through Albert S. Osborn's carefully worded paragraph.
The eight experts who testified that Hauptmann was the writer of the questioned documents, comprised a whos-who in the field. They were:
- Albert S. Osborn, New York City
- Albert D. Osborn, New York City
- Elbridge W. Stein, Montclair, New Jersey
- John E. Tyrrell, Milwaukee
- Harry Cassidy, Chesapeake & Ohio RR, Virginia
- Herbert J. Walter, Chicago
- Dr. William Souder, National Bureau of Standards
- James Clark Sellers, Los Angeles
The testimony of these experts, more than any other aspect of the prosecution's case, shifted the burden of proof to the defense. It was now up to Hauptmann to prove to the jury of four women and eight men, a group of high school educated, common sense people, that he was innocent. It would be a tough sell.
To counter the prosecution's powerful documents case, Hauptmann's lead defense attorney spoke to a dozen or so possible handwriting witnesses, two of whom refused to testify for the defense because it looked to them that Hauptmann had written the ransom notes. The others were so patently unqualified, or mentally unstable, they were kept off the stand by the defense. The lone handwriting witness for Hauptmann, John Trendley of St. Louis, was exposed, on cross-examination, as a courtroom charlatan. As a result, the four prosecuting document examiners standing by to testify in rebuttal, weren't needed. These experts were:
- John Vreeland Haring, New York City
- J. Howard Haring, New York City
- Joseph Schulhafer
- Bert C. Farrar, U.S. Treasury Department