The technique of fingerprinting is known as dactyloscopy.To create an ink fingerprint, the person's finger is first cleaned with alcohol to remove any sweat and dried thoroughly. The person rolls his or her fingertips in ink to cover the entire fingerprint area. Each finger is then rolled onto prepared cards, from one side of the fingernail to the other. These are called rolled fingerprints. Finally, all fingers of each hand are placed down on the bottom of the card at a 45-degree angle to produce a set of plain (or flat) impressions. These are used to verify the accuracy of the rolled impressions.

    Ever since scientists discovered that every person's fingerprints are unique, and police officers realized this singularity could help them catch criminals, fingerprints have been an integral part of the law enforcement process. Today, fingerprints are also used to prevent forged signatures, identify ­accident victims, verify job applicants and provide personalized access to everything from ATMs to computer networks.

But fingerprinting has come a long way from the days when police officers lifted prints from a crime scene and checked them manually against their files. Modern fingerprinting techniques can not only check millions of criminal records simultaneously, but can also match faces, backgrounds and other identifiable characteristics to each subject.