Fingerprint evidence, although sometimes not as high-profile
as other high-tech crime-solving methods like DNA typing, is still very much
used in criminal investigations and cases. While the principle that no two
people can have the same fingerprints cannot be scientifically validated,
fingerprint evidence is generally considered to be highly reliable and is
particularly accessible to juries: You don't need a Ph.D. or a scientific
lecture on genetics to understand that your own fingers contain a contour map
of ridges and whorls that is completely unique.
Fingerprint evidence rests on two basic principles:
1. A person's
"friction ridge patterns" (the swirled skin on their fingertips)
don't change over their lifetimes.
2. No two people have
the same pattern of friction ridges. Even identical twins have different
fingerprints.
Police officers use fingerprints to identify defendants by
comparing prints found at a crime scene with prints already in police files. Fingerprints can filed for a many reasons. For example, people
may be fingerprinted when they are arrested or when they begin certain
occupations.
Friction ridges contain rows of sweat pores, and sweat mixed
with other body oils and dirt produces fingerprints on smooth surfaces.
Fingerprint experts use powders and chemicals to make such prints visible. The
visibility of a set of prints depends on the surface from which they're lifted;
however, with the help of computer enhancement techniques that can extrapolate
a complete pattern from mere fragments, and laser technology that can read
otherwise invisible markings, fingerprint experts increasingly can retrieve
identifiable prints from most surfaces.
The age of a set of fingerprints is almost impossible to
determine. Therefore, defendants often try to explain away evidence that their
fingerprints were found at crime scenes by testifying that they were at the
scene and left the prints at a time other than the time of a crime.
With the pros and cons that this type of expert evidence comes
with, do you still think that it can still be considered a reliable method? Hope to get feedbacks soon
! :)
Reference : Fingerprint Evidence in Criminal Cases (http://www.nolo.com)