8127/frame/fm

 
Figure 11.5
Dilutions. In chemistry 101 we are taught the fundamentals of
significant figures. This is an example of thoughtfulness put on hold.
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Principles and Practice of Criminalistics
However, the preceding is not always the outcome. The following is an
example involving serological typing and DNA.
A private consultant was asked to review a DNA report from a private
laboratory regarding an attempted rape. The initial serological screening
was performed by a city laboratory, and a number of different evidence
items were selected to forward for DNA analysis. One of the items, an
apparent bloodstain taken from the defendant’s car, was determined by
DNA to show the same markers as the victim, and the laboratory submitted
a report to this effect. However, nobody, either at the DNA laboratory or
from the originating laboratory, bothered to compare the two reports. If
they had, they would have noticed that the victim was 
 
excluded
from con-
tributing to this stain by ABO typing. Like most instances of this type, more
work could have probably resolved that apparent discrepancy. As it was, the
defendant obtained a plea-bargain for a substantially reduced sentence.
A major case file with lots of evidence will frequently contain reports
from several different individuals covering a number of disciplines. These
analyses may have been performed in a complete vacuum relative to each
other, potentially compounding the problems described above.
Surprisingly few laboratories seem to have a formalized system for inte-
grating interdisciplinary analyses from a single case (Zeppa, 1999). No one
person reviews the entire case file and looks to see if the evidence appears to
tell a coherent story. If contradictory results exist, the attorney and the
investigator are left to sort things out. We would like to suggest that the final
element of good laboratory practice is to generate a comprehensive report
summarizing the results of all the different examinations and analyses. Such
a report would provide a complete picture of the physical evidence in the
case and lay the foundation for a reconstruction — the ordering of events
(as defined by physical associations) in time and space.