The formal documentation of the alteration attempt and its failure — including the internal FBI memo noting the “unexplained differences” and attributing them to acid, the positive identification from surviving ridge areas, and the subsequent academic analysis by Harold Cummins — became reference material in the technical literature.
The 1935 Journal of Criminal Law and Criminology article, authored by researchers studying fingerprint alteration following the Dillinger case and similar cases, examined the biology of print formation and the specific mechanisms by which surface treatments failed to produce permanent alteration. The article’s finding that at least one millimeter of skin removal was required to have any chance of obliterating the dermal template reflected the technical understanding of print formation that the Dillinger case had helped publicize.
The Hoover-commissioned 1934 committee report — the one that examined whether fingerprints could be permanently obliterated and concluded they could not by the methods available to criminal operators — was used in the Bureau’s public communications about forensic capability. The Dillinger case was the organizing example.
What the case illustrated, and what remained relevant in subsequent decades as the FBI fingerprint identification infrastructure expanded, was the relationship between evidence of alteration and evidentiary value. An altered fingerprint is not worthless. A damaged print can still identify a person if sufficient ridge detail survives in any part of the finger surface. And surface-level alteration reliably leaves residual ridge detail somewhere on the fingertip.
The peripheral ridges — the areas toward the edges and margins of the fingertip that receive less concentrated treatment in typical acid applications — are particularly durable. The tendency to focus chemical attack on the central pattern area, where the distinctive loop or whorl core is located, leaves the margins relatively intact. Those margins contain continuous ridge detail that connects to the same pattern and can be matched to known records.