What method did John Dillinger attempt to use to remove his fingerprints?

John Dillinger attempted to remove his fingerprints using acid. This method involves the application of strong caustic substances to the skin, with the idea that these substances could effectively destroy the unique patterns of the skin ridges that form fingerprints. Dillinger's actions reflect an extreme effort to evade law enforcement, as fingerprints are critical for identification in criminal investigations.

While there are various other methods that might be theoretically proposed for altering fingerprints, such as laser treatment or extreme heat, Dillinger's choice of acid demonstrates a more direct and historically documented approach to this problem in the context of his criminal activities.