In earlier civilizations, branding and even maiming were used to mark the criminal for what he was. The thief was deprived of the hand which committed the thievery. The Romans employed the tattoo needle to identify and prevent desertion of mercenary soldiers. More recently, law enforcement officers with extraordinary visual memories, so called camera eyes identified old offenders by sight. Photography lessened the burden on memory but was not the answer to the criminal identification problem; personal appearances change. Fingerprints offer an infallible means of personal identification. That is the essential explanation for their having supplanted other methods of establishing the identities of criminals reluctant to admit previous arrests. Other personal characteristics change- fingerprints do not.