Two Basic Principles of Fingerprinting

Persistence

Fingerprints never change. If you draw a face on an uninflated balloon, then fill the balloon with air, the features of the face will grow with the balloon as you blow it up. Fingerprints are similar in that they remain permanent, only growing larger as a baby grows into an adult. The small ridges that form on a person’s hands and feet before birth do not change shape as long as that person lives.

Uniqueness

No two fingerprints are alike. The ridges on a person’s hands and feet have distinctive, individual details that are never repeated on the hands or feet of any other person. In more than 100 years of comparisons of billions of fingerprints worldwide, no two fingerprints have been found to have the same features. Even identical twins have different fingerprints.

Found within the 2014 printing of the Fingerprinting Merit Badge pamphlet