"Scientific Criminal Investigation Progress"
By Herman B. Davis
As Director of the Kansas City Missouri Police Crime Laboratory during the mid 40's to
the late 60's, I was asked to submit a copy of our policy guidelines which
we were using. The following copy was submitted to be included in a policy
manual for the entire department:
"Any member of our staff who reaches a conclusion about an
identification, or a fact as a result of a criminal investigation shall
immediately construct a demonstrative exhibit showing, graphically the
characteristics which gave rise to the conclusion. This exhibit shall then
be presented to at least one member of the staff for constructive
criticism or concurrence."
This policy was readily accepted by the staff with one exception. The
polygraph operator used the chart produced by the machine, and verbally
explained the reactions to questions. It was my duty to review these
cases, and I immediately determined that his explanations were entirely
subjective. Therefore, this phase of criminal investigation was dependent
upon one person, and was capable of error. Because of this I recommended
transfer of the polygraph phase of the laboratory operation. This was
immediately done. The polygraph was transferred to the detective division
where the policy governing the polygraph operation appeared to be: "If our
prime suspect can pass the polygraph test, walk him, and list our case as
I attended the organizational meeting of the American Academy of
Forensic Science in St. Louis in 1947, and attended all annual meetings
after that until I retired. During the last year of my employment there
were repeated debates, discussions and suggestions that we use DNA tests
in our criminal investigations work. There were always pros and cons.
Generally speaking, the test was considered to be capable of error. My
concern was that our investigative forces would tend to treat DNA like
they did the polygraph test; use DNA testing on our prime suspect, and if
his pattern does not agree with that of the crime scene, walk him, and
mark his case inactive.
Recently, in Kansas City, Missouri in a criminal court trial for
homicide, the state's DNA expert testified that the DNA pattern from a
hair agreed with that of a victim. The defense's DNA expert testified that
his DNA examination of that same hair did not agree with that of the
We must now, therefore, conclude that DNA testing is capable of error,
because one expert in that courtroom has to be in error, they can't both
We must in our criminal investigation work give careful consideration
to all of our test information if we are going to see that the process of
justice is accomplished.
During my time in the laboratory one of my reports was challenged. The
prosecuting attorney said, "How do you explain your statement that the gun
was in contact with the victim when it was discharged, while the
pathologist reports that the gun was 10 inches away?"
I recovered my exhibit from the file. (See
Photographic Evidence by Charles C. Scott Vol.1 p. 523). The pathologist
admitted that my conclusion was indisputable, thus proving the value of
the exhibit. We must, therefore, always support our findings with evidence
that is not subject to serious challenge. We cannot rely upon any test
with a capability of error.
October 9, 2002