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Figure 2.3
 
Homunculus.
In the early days of microscopy, analysts believed that
they could discern a little man in the spermatozoa that would later grow and
emerge from the uterus as a human being. Later advances in the manufacture of
microscope lenses, and in our knowledge of biology, would suggest a slightly
more complex mechanism for the propagation of life.
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34
Principles and Practice of Criminalistics
reliable protocols for the typing of polymorphic protein and enzyme markers
to the United States and worldwide.
Although the ability to type biological material had been available for
much of the 20th century, a dermatoglyphic fingerprint was still considered
the ultimate in human identification. That all changed abruptly in the mid-
1980s when Sir Alec Jeffreys initiated the greatest advance since Landsteiner
with his discovery of “multilocus” restriction fragment length polymorphism
(RFLP) testing (Jeffreys et al., 1985). During its adoption for use by the FBI
and others, the testing was modified to test one locus at a time, and eventually
more than a dozen markers became available for standard forensic testing.
Around the same time, another invention revolutionized not only forensic
DNA typing, but the very face of molecular biology. In 1983, Kerry Mullis
conceived the idea of the polymerase chain reaction (PCR) while driving on
a lonely highway to his backwoods cabin (Saiki et al., 1985; Mullis et al.,
1986). The idea was introduced at Cetus corporation, where he was
employed, and subsequently developed by the human genetics group there
led by Henry Erlich. Because PCR can selectively amplify any desired region
of the genome, it was an obvious choice for minute, degraded forensic sam-
ples. All of the genetic systems developed for forensic DNA typing since then
depend on PCR as an initial step.
Although the potential to individualize using DNA has always been
apparent, it was not fully realized with the earlier systems, in particular the
first PCR-based markers. Ironically, Jeffreys’ original multilocus “DNA fin-
gerprint” probably was individualizing. Today, most scientists would agree
that a 6 to 9 locus RFLP profile effectively supports an opinion of a one-to-
one correspondence between a stain and a donor. Nevertheless, the capability
was immediately apparent and the obvious possibilities sparked a scrutiny
and challenge to which a forensic technique has never before been subjected.
Once Pandora’s box was opened, the scrutiny turned toward other disciplines
of forensic science, provoking, for the first time in history, a mobilization of
the profession as a whole. While formal standards and quality assurance
measures such as analyst certification, laboratory accreditation, and educa-
tional standards had long been promulgated by small groups within the
profession, the greater forensic science community was now impelled to
embrace such measures formally. DNA laboratories have begun to implement
the newest genetic system, short tandem repeats (STRs), along with a uni-
versal move toward automation, allowing more than a dozen DNA markers
to be analyzed in just a couple of runs. A moment of clarity occurs when we
realize that, more than a century later, DNA typing is close to being accepted
as individualizing evidence of 
 
who?
with the confidence that has almost
automatically been accorded to fingerprints for almost a century.
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The Evolution of Forensic Science
35