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                   a bit on the science of fingerprinting
                   ------ by William JB Cross | PI ------


TO THOSE INVESTIGATORS WHO UTILIZE THE FIELD OF FINGERPRINTS IN THEIR WORK:

A quick tip:  remember that any fingerprints left at a scene are of little
value without the benefit of at least a strong suspect in most cases.  

Unknown prints left at a scene must be compared to the fingerprints of a
suspect.  These latter prints are referred to as "known" prints.  In a
police investigation, unknown prints (if of the required quality) can be
entered into an AFIS (or similar) computer system and a search can be made
electronically to find a possible match.  Of course, a match will only occur
if the suspect has had his/her prints entered into the system (eg: by way of
a criminal charge/conviction or other).  However, in the Private
Investigation field, these resources for matching prints are usually not
available.  Thus, without a suspect, unknown prints left at a scene can be
of little value without the assistance of law enforcement agencies who could
search the unknown prints for you-very unlikely.

Keep in mind though, that if good quality latent prints were found at a
scene, and it was possible to obtain the prints of a strong suspect, a
"match/ident" between the unknown prints and those of the suspect could
prove to be invaluable evidence concerning a case.  With properly developed
and recovered latent prints (where the minutiae is clear) a competent latent
print examiner should have no difficulty making a "match" between unknown
and known examples.

Also, always remember when collecting evidence at a scene to document and
photograph all items (if possible) before attempting to recover/remove such.
Always maintain an unbroken "chain of continuity" regarding any evidence
recovered.  This means that you MUST keep a detailed record of where
recovered items of interest are/have been since the moment such was
discovered until after the case has been closed.  Naturally, this record
must also reflect who has had possession of the evidence since its discovery
(along with any other pertinent information).  Once the chain of continuity
is broken, the value of any evidence diminishes greatly.

By keeping the aforementioned points in mind, your investigations involving
fingerprint evidence will certainly be more successful.

William J.B. Cross, LPE
CROSS IDENTIFICATION LABORATORIES
Milton, ON
Canada
wcross@interhop.net


Sidenote by mechanic: This may seem to some of you out there that this is a 
                      little off the DMS topic, well, it's not. We are here
                      to keep people informed, and this is exactly what this
                      article is doing.