Classifying Fingerprints

As you’ve probably learned in the previous activity, it is difficult to identify fingerprints. They are rather small and contain a lot of detail. To simplify their identification process, forensic scientists use a classification system. Try the following activity and learn to classify fingerprints.

Materials
- magnifying lens
- several sets of fingerprints, your own and those of helpers

Procedure
1. Use the magnifying lens to observe several sets of fingerprints. Do you notice characteristic that any of them share? Can you group the prints into categories to make the identification process easier?
2. Look at the common fingerprint patterns in the diagram. Notice that arch and the loop can have several forms and may bend to the right or the left.
3. Try to match the fingerprints that you have collected to one of the common patterns.

Explanation

There are several ways to classify fingerprints. In this activity, you have tried one of the easiest ways. More complex classification systems break down the common fingerprint pastern into smaller groups. For example, forensic scientists divided arches into plain arches (arches that are rounded) and tented arches (arches that are pointed). Loops can be either radial loops, which loop from the right, or ulnar loops, which loop from the left. Similarly, whorls are classes into several subdivisions.

Even more complex classification systems, such as the Henry System, have been developed to help compare fingerprints. The Henry System use a number system to classify the characteristics of a fingerprint as well as the type of finger and hand from which it came. Investigators match a fingerprint to a person by matching the print’s numbers to others prints with the same numbers, rather than by individually comparing a suspect’s fingerprint to every fingerprint on file.

Fingerprints used to be examined and classified by hand. This was a slow, time-consuming process. Now computers can scan a fingerprint and compare it to huge files that have been collected from many police agencies, such as the FBI. This system, called AFIS (Automatic Fingerprint Identification System), can do the work in a fraction of the time. For example, it takes AFIS only two minutes to complete a fingerprint comparison that used to take years to complete by hand.

There is one limitation to AFIS and all fingerprint identification methods. Although there are cover 250 million people in the United States, there are only about 10 million sets of fingerprints on file in AFIS. If a criminal’s fingerprints are not on file, the system does nor work.