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d.
Significant Figures
This is a relatively harmless complaint, but does go to the thoughtfulness of
the analyst. We are all taught in Chemistry 101, if not long before, that no
numerical weight or measure should be written with more significant digits
than is reflective of our actual confidence in the accuracy of the measurement.
For some reason, when calculators, and now computers, are used to make a
calculation, people tend to record the number that flashes on the screen with
absolutely no regard for whether the last 10 digits provide any meaningful
information. Is the weight of the cocaine sample really accurate to five digits
(1.3572 g) or is the scale only accurate to two digits (1.4 g). Can we really
estimate a population frequency to four significant digits (0.1383) or is a
more reasonable representation two digits (0.14). An example of an institu-
tionalized misappropriation of significant figures by a company who should
know better is shown in Figure 11.5. We make a plea here to apply some
intelligent thought to the number of significant digits you record both in
your notes and in your report. You will lose at least one opportunity to look
silly on the stand when opposing counsel asks you if you can really measure
the concentration of DNA in your tube to five significant figures.
 
2.
The Big Picture
At one time, the same person who performed the blood typing would simply
move over to another bench to examine fibers under a microscope or to
compare two dermal ridge prints. At most, another analyst in the same lab-
oratory might participate in analyzing the evidence in a single case. This is
no longer the situation. It is not uncommon these days for various pieces of
evidence in a case to be examined by multiple analysts in the same laboratory,
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Communicating Your Results — Where Science Meets the Law
285
multiple laboratories, multiple jurisdictions, or even public and private lab-
oratories. The detective and ultimately the attorney is then left with numer-
ous reports from different people in various disciplines, and no way to
integrate the results into a meaningful whole. Many of the analysts who did
the work may not have any expertise beyond their individual specialty. We,
as workers in the field, need to think about how best to integrate this pro-
fusion of information and help those in the legal system who ultimately use
our work product to understand how all the evidence fits together.
Things have gotten so specialized that disciplines that were once consid-
ered one have become distinct entities. This can cause problems when the
analysts no longer speak the same language and in effect have stopped com-
municating with each other. We even know of one case in which analysts
from the same DNA laboratory, analyzing literally the same piece of evidence,
failed to communicate with each other, with potentially disastrous results.
Different cuttings from the same panty crotch were analyzed within a single
DNA laboratory by individual analysts using different genetic marker systems.
None of the analysts was aware of the results of any of the others, or of the
initial serology results from the submitting laboratory. Each analyst was about
to submit an isolated report, when an alert reviewer realized they were all
from the same case, and that the typing results appeared to be internally
inconsistent. Fortunately, after reviewing the history of the evidence and the
case circumstances, the reviewer was able to reconcile the apparently discrep-
ant results before the situation created any more confusion.