At the Lindbergh-Hauptmann trial, eight nationally known questioned document examiners, from Los Angeles to New York City, both private and government employed, testified that Hauptmann wrote the fifteen ransom letters, including the note left by the kidnapper in the baby's nursery. The Lindbergh crime produced an unusually large quantity of questioned writing. Moreover, the experts had plenty of known handwriting to work with in the form of request writings--a carefully worded paragraph dictated to Hauptmann--and his conceded or "course of business" writings in the form of his personal notebooks and his auto registration, driver's license, and insurance applications.
The prosecution experts testified that Hauptmann's known writing looked like the writing in the ransom documents. They produced dozens of word chart exhibits for the jury that illustrated the similarity in the two sets of cursive writing. Hauptmann and the ransom note writer also misspelled certain words the same way.
The questioned document testimony phase of the Lindbergh-Hauptmann trial took up four days and produced 800 pages of trial transcript. Besides the eight experts who took the stand, the prosecution had four rebuttal experts who would have testified against Hauptmann had the defense put on a credible battery of their own handwriting witnesses. As it turned out, these rebuttal witnesses were not needed.
One the the rebuttal witnesses, John Vreeland Haring, later published a heavily illustrated book showing why he believed Hauptmann had written the ransom documents. Mr. Haring made a special effort to illustrate the similarities between the defendant's writing and the ransom note left in the nursery. For comparison purposes, Haring used as known handwriting samples, two post-conviction letters Hauptmann had written in hand to the Governor of New Jersey.
In addition to the prosecution's eight handwriting witnesses and the four rebuttal experts, Charles A. Appel, Jr., the head of the FBI crime lab, believed Hauptmann was the ransom note writer. While he didn't testify at the trial, the FBI crime lab director testified against Hauptmann before the Bronx Grand Jury months before.
Hauptmann's defense attorney, Edward J. Reilly, asked seven document examiners to look at the handwriting evidence. Three declared that Hauptmann had written the documents, another three said the ransom notes had been altered after Hauptmann's arrest to look like his known writing--thereby conceding that the known and questioned writings were similar. The seventh examiner asked by the defense to analyze the evidence, a man named John C. Trendley from St. Louis, ended up being the only examiner who actually testified for the defense at the Hauptmann trial.
A reporter who covered the Lindbergh-Hauptmann trial wrote this about Mr. Trendley: "He was a furtive, musty little codger who had the greatest difficulty establishing his claim to be an expert...And his testimony was really pathetic." Besides his background as a courtroom charlatan, Trendley's testimony was weakened by the fact he had not spent much time with the evidence.
Hauptmann's defense lawyers--he had five--were never able to counter the prosecution's overwhelming handwriting case against their client. Notwithstanding all of the other physical evidence connecting Hauptmann to the crime, it was his handwriting that sent him to the electric chair.
To this day, the Lindbergh case remains the high water mark in the American history of forensic document examination.