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ii.
Biological evidence.
Once the fluid or stain is collected, the goal is to
preserve it in the laboratory both to prevent degradation and contamination.
The two most important elements needed to accomplish this are the reduc-
tion of both moisture and temperature. Any item collected in liquid or wet
form is quickly dried. Evidence should be placed in a non-frostfree freezer
for long-term storage.
 
4.
Contamination
Although the specter of contamination is frequently used as a weapon, the
subject is rarely discussed from a serious and neutral standpoint. We therefore
include a relatively extended treatment here.
 
a.
Definition of Contamination
 
Contamination
, which we fondly refer to as the C-word, is in actual fact a
catchall buzzword for a number of different situations. Like the proverbial
“weeds are plants where they are not wanted”, contaminating material seems
to be anything that anybody deems confounding to a forensic analysis. Each
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Good Field Practice — Processing a Crime Scene
211
situation has different consequences for handling and interpretation. As with
all forensic issues, the interpretation of “contamination” depends on — 
The
Question.
For example, it is discovered that bedsheets show the genetic type of
more than one person. One could ask, who was the last person to leave
evidence on the sheet? Some might argue that, should multiple types be
detected, the ones they don’t like or don’t think should be present should be
considered contamination, or at least an interfering element in the analysis.
Another question one could ask would be, who are all the persons that ever
left evidence on the sheet? In this case, all the types that might be found on
the sheet are integral to answering the question. Either way, the material
contributing to the types was all present before a crime scene was ever
identified.
A contrary example is found in the 
Simpson
case (
People v. Simpson
,
April 5). A blanket from Nicole’s house was reportedly used to cover her body
in an effort to provide privacy from the media. The intention was commend-
able, but it rendered any examination for trace evidence on the body com-
pletely useless. What was relevant to the crime? What came from the blanket?
The difference between this example and the previous one is that material
known to be extraneous to the crime was introduced by responsible personnel.
Because the word 
contamination
is widely co-opted to describe so many
situations, no widely accepted definition exists. 
Webster’s
(1996) defines con-
taminate as “to make impure or unsuitable by contact or mixture with some-
thing unclean, bad, etc.” Because all evidentiary material is by nature impure
(it’s always in contact or mixed with something), the question becomes,
which impurities would render the sample unsuitable for analysis and correct
interpretation?
Just as misleading as the dictionary definition, the term has acquired a
negative connotation among the public, namely, that a contaminated sample
is inherently an untrustworthy sample. Raising the specter of 
contamination
is a convenient and simplistic way of dismissing the results of an analysis.
This is both disingenuous and misleading. We reserve the word “contamina-
tion” for those circumstances where improper or careless handling by those
responsible for collection, preservation, or analysis has accidentally intro-
duced extraneous substances into the evidence sample. A good working
definition might be: