How are fingerprints made visible, collected, and analyzed?
Fingerprints are a unique individualizing characteristic of humans. Even identical twins will
have different fingerprints. Fingerprints are formed while a person is still in the womb and
are due to friction of the individual in their environment. Once formed, fingerprints will
hind an imprint of your skin, sometimes it’s visible, sometimes it’s not, but it is there, wait-
ing to be found.
▪ Students will be able to identify the difference between latent and visible prints.
▪ Studcollection.e able to distinguish between the techniques used to expose latent prints for
▪ Students will be able to analyze fingerprint patterns, using both common types and minuti-
ridges are formed underneath the skin and as long as the dermal layer stays in-tion
tact, the skinprints stay the same and will come back after injury.
These prints are left behind as impressions into a surface or deposited as a thin
film of water and oils secreted by the body. Making a print visible means react-
ing with the depositions left behind.
There are basic types of fingerprints as well as numerous minutiae that are used
to categorize fingerprints.
▪ Individual vs. Class characteristics
Saferstein, 8 edition, pg. 406-429
Model 1 : Visible vs. Latent Prints
For a given set of circumstances, the choice of the best detection techniques, or sequence of
techniques, will depend on several factors that include: the nature of the surface (eg, porous, non-
porous, rough or smooth); the presence of any particular contaminants (eg, blood);
environmental factors (eg, whether or not the surface is or has been wet); and, the likely age of any
In any fingerprint detection sequence, heavy emphasis should be placed on optical techniques, as
these are non-destructive and may significantly improve the results obtained by physical or
chemical methods. Other techniques must be applied with caution, and developed prints recorded
at each opportunity, as fingermarks are fragile and readily destroyed.
Techniques for Visualization Collection as Examples
▯ • Dusting : suitable for hard or non- Once visualization -Any skin
Latent porous surfaces only where the is complete, the surface that
secreted oils will sit above the print is has come into
surface and adhere the dust to photographed and contact with
create a liftable print lifted with an another solid
• Luminescence : some components evidence card that surface
of sweat are luminescent and has tape attached to allowing the
fluoresce when illuminated with a cardboard transference
lasers. Also, fluorescent dyes can backing, often of natural
be employed that do not require marked with the oils and sweat
laser excitation. metric system scale from the
• Iodine fuming or Physical body
Developers (silver nitrate): suitable
for a porous material where the
oils have been absorbed. The
iodine is believed to dissolve in the
skin oils that make up the print
(temporary and will fade).
• Ninhydrin: suitable for a porous
material where the oils have been
absorbed. A Colorless compound
reacts with amino acids in sweat to
form a purple colored compound.
• Superglue fuming: suitable for hard
or non-porous surfaces only where
the secreted oils can come into
contact with the Cyanoacrylate
ester and polymerize. The visible
prints produced are white, but are
often treated with a fluorescent
dye to improve visibility. ▯ No need for a visualization The print is - Skin