1. How are fingerprints used in Forensics?
Fingerprints are impressions that are left on surfaces in the oil which is deposited by a persons touch.
Every living person has a unique pattern of ridges and depressions on the tips of their fingers. This makes it possible to positively identify an individual victim or criminal or prove the presence of a suspect at a crime scene.

2. History
The principle of fingerprint was recognized three thousand years ago in ancient China, where it was common for legal contracts to be endorsed by the fingerprints of the parties involved.
This custom was also adopted by the Japanese.
In the 1900’s, William Herschel introduced contracts “signed” by the print of the signatory’s right hand.
First group to use computer stored fingerprint records was the Royal Canadian Mounted Police in the mid-1970’s.
Finger print records can now be scanned at tens of thousands of prints per second.

3. Collection
Fingerprints found at a crime scene fall into three main categories:
Visible
Easiest to spot
Made by fingers that have been in contact with paint, ink, blood, etc…
Plastic
Made by fingers pressing into a soft surface
Latent
Most common & hardest to see
Made when natural oils & perspiration are transferred to a surface by touch
Magnetic powders and tape
Dust them with a powder.
White powder is used on dark surfaces.
Dark powder is used on light-colored surfaces.
Ninhydrin spray turns purple in contact with human amino acids.
Silver nitrate reacts with salt in perspiration forming silver chloride and is revealed under UV light.
Fuming with super-glue relies on cyanoacrylate ester.
Fuming with iodine for lifting prints from fabrics.

4. Categorization Patterns of ridges on the surface.
Three basic types of fingerprints:
Loops (2/3’rds of population have loops)
Radial
Ulnar
Ridges/Arches
Plain
Tented
Whorls (almost 1/3’rd of population has whorls)
Double Loop
Central Pocket Loop
Accidental

5. Comparison Visual identification
Computer recognition (American Fingerprint Identification System AFIS)

6. Reliability
No two persons have the same patterns of ridges and depressions.
With a high quality print and a known set of prints for comparison, such as a victim or AFIS data base, positive ID of a body, suspect, or individual’s presence at a crime scene is possible.
Without a known set for comparison, fingerprints can provide direction for an investigation.

7. Additional Applications for Using Fingerprints
Child-find kits
Pre-employment background checks
Security clearance
Secure accessibility for door entrances, computers, etc…

8. Resources
Hidden Evidence by David Owen, Firefly Books, 2003, pp
Crime Scene Investigations by Pam Walker & Elaine Wood, The Center for Applied Research in Education, 1999, pp. 3-10
Poster - “Fingerprint Classification Chart” Ward’s Natural Science – designed by Robert Verni