Each class can be further divided into numerous sub-categories. In addition to overall patterns, there are many minute variations and irregularities in the ridges themselves. Each print has its own unique combination of overall pattern and special ridge characteristics. No two prints have ever been found that were exactly alike. Even those of identical twins are different.
Prints remain the same throughout life.
When prints are found, an expert compares them with samples known to have been made by a suspect. The prints you find at a crime scene aren't always complete. This doesn't keep them from being used for comparison. What counts is the number of points of comparison. A partial print from just one finger may be all that's necessary.