That case study remains relevant in a world where fingerprint technology has advanced substantially since 1934. Modern automated fingerprint identification systems — AFIS, the successor to the manual card files of the Bureau’s 1930s Identification Division — can process far more data at far greater speed than any human examiner working manually. The database of fingerprint records maintained in the United States now contains hundreds of millions of records, compared to the millions available in 1934.
The fundamental biology has not changed. The ridge patterns originate in the dermis. The dermis retains its template even when the epidermis is damaged. The peripheral regions of a chemically treated fingertip survive at higher levels of legibility than the central regions. These biological facts, documented specifically in the Dillinger case and subsequently confirmed across dozens of additional cases, remain the basis for the conclusion that fingerprint alteration as commonly practiced does not defeat identification.
What has changed is the precision and speed of comparison. Modern AFIS systems can identify partial prints, damaged prints, and altered prints with greater reliability than the manual comparison methods of 1934. The same biological reality that allowed a 1934 examiner to identify John Dillinger from damaged peripheral ridges is now exploited by systems capable of searching hundreds of millions of records in seconds.
—
## The Testimony of the Guns
A detail of the Biograph shooting that received less attention than the fingerprints but that contributed to the identification record was the firearm Dillinger was carrying.
He was armed with a Colt .380 automatic pistol when he emerged from the theater. Some accounts describe the weapon as a .38, the two calibers being similar enough to generate confusion in contemporaneous reports. The specific firearm was not in question as a piece of evidence; Dillinger’s possession of a firearm on the night of July 22 was consistent with his known practice throughout his criminal career.