"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 inactive."

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 victim.

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 be right.

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

Reprinted with Permission