Fingerprint background
What is a fingerprint?  It is technically a reproduction of friction skin ridges.  Our fingers (and indeed all our skin) is made up of hills and valleys or ridges.  These ridge characteristics, called minutiae, are formed before birth and remain unchanged through death. Not even twins have the same pattern. Positive proof of identification involves a point-by-point comparison of the minutiae. The pattern of the minutiae are how we determine the individuality of a print.   A ridge count is done across an imaginary line on the delta.  The delta is an intersection of ridges.  There are several ridge classifications that will be viewed in lab.

The fact that prints are formed before birth is significant.  It has been found that there is a scientific relationship between actual and projected birth date and the type of predominant print.  Loops are found in 65% of the population, which is the approximate percentage of on time births.  Whorls, found in approximately 30% of the population, are associated primarily with premature births.  Arches, the last 5%, is found in overdue babies.  This study has held up in the classroom as well in official lab studies.

Fingerprints are also classified by the way they are found.  Latent fingerprints refers to prints that are not easily seen.  Visible prints, called patent prints, can be seen right away becsause they are formed by other materials like blood.  Fingerprints in soft surfaces, like wax, are called plastic prints.   Smears are when pressure has been applied as the print is being formed.  Other types of prints occur besides fingerprints and have their own name.  Plantar prints refer to footprints.  Palmar prints refer to prints caused by the palms of the hands.  Most prints are formed by dirty fingers because we don't have sweat glands on our fingers.  Oils from other body areas, dust, and other materials collect on our fingers and allow us to leave this subtle trace of ourselves.