The Molecule of Life on Center Stage
Much of the November 6th status hearing dealt with evidence issues, with the Defense requesting that the Government be required to turn over the lab notes of the technicians, in addition to DNA test results and the methodologies used. DNA evidence has been used to both convict and exonerate defendants.
It remains controversial in the United States for reasons that include disagreement on the appropriate methodology used to test the DNA, DNA evidence collection errors, laboratory procedure errors, and disputed statistical conclusions from various forensic biologists.
Let us examine where the defense team may be going with their insistence on obtaining all data, including laboratory bench notes from the FBI forensic testing:
1) Testing Methods – While a certain amount of judgment may be used by the lab in determining the appropriate tests to use to on the DNA sample, there are generally accepted tests that have become standards depending on the size and condition of the sample. Discussion of these techniques can be found in many references including a University of Michigan course “DNA Fingerprinting, Genetics and Crime: DNA Testing and the Courtroom”, “DNA Testing: An Introduction For Non-Scientists” from Scientific Testimony, and “DNA Profiling” from Wikipedia. The Government has turned this information over to the Defense, and so far no motions have been made regarding the validity of the methods used. Of course, the Defense may be waiting for Dr. Lee’s return from his travels.
2) Collection and Handling – The collection of DNA samples is a critical, initial step in its potential use as evidence. Law enforcement agencies have documented processes and procedures, however, these are vulnerable to human error and judgment. Evidence may be overlooked or contaminated. The MPD’s mishandling of Robert Wone’s BlackBerry and the abhorrent conditions at the Evidence Control Facility provide the Defense team with many opportunities to refute admissible evidence.
3) Laboratory Procedures – Human error is generally considered to be the most frequent cause of erroneous DNA evidence determinations. The problem that presents itself is that humans are involved in virtually every step of the testing process, from sample handing, laboratory procedures, determination of results, and case review. Guidelines for quality assurance and quality control have been developed and implemented at most laboratories, but that does not preclude human error, only reduces it. From “The Evaluation of DNA Forensic Evidence”:
“The occurrence of errors can be minimized by scrupulous care in evidence collecting, sample-handling, laboratory procedures, and case review. Detailed guidelines for QC and QA (quality control and quality assurance), which are updated regularly, are produced by several organizations…”
One common guideline is that laboratory testing personnel must maintain and file notes and observations along with the types of procedures used and conclusions. Because human error has the potential to bungle test results, the Defense has clearly focused its approach to uncovering any questionable practices or conclusions reached by the lab technicians, hence their demands for laboratory notes. By introducing doubt, the Government’s case may crumble.
4) Statistical Issues – Quantitative analysis, i.e. statistics, have been used in every field to prove or disprove theories. A popular book used in many stats classes is “How to Lie with Statistics” by Darrell Huff. Huff outlines common errors, both intentional and unintentional, associated with the interpretation of statistics, and how these errors can lead to inaccurate conclusions. DNA results rely on quantitative analysis, and are subject to interpretation. In the Wone case, linking an intruder versus one or more of the defendants to the crime scene via DNA testing is critical evidence for both the Defense and the Government. As discussed in “Evaluation of DNA Forensic Evidence”:
“Suppose that a DNA sample from a crime scene and one from a suspect are compared, and the two profiles match at every locus tested. Either the suspect left the DNA or someone else did. We want to evaluate the probability of finding this profile in the “someone else” case. That person is assumed to be a random member of the population of possible suspects. So we calculate the frequency of the profile in the most relevant population or populations. The frequency can be called the random-match probability, and it can be regarded as an estimate of the answer to the question: What is the probability that a person other than the suspect, randomly selected from the population, will have this profile? The smaller that probability, the greater the likelihood that the two DNA samples came from the same person. Alternatively stated, if the probability is very small, we can say that either the two samples came from the same person or a very unlikely coincidence has occurred.”
By introducing expert testimony that interprets test results differently than the Government laboratory, the defense can once again introduce doubt to the juty.
But does any of this make the defense strategy unique? From all appearances, these scenarios have been played repeatedly in courtrooms around the world. Norah Rudin, Ph.D., Forensic DNA Consultant, has published the following guide for attorneys:
The Defendants’ motions to compel discovery of the lab notes, etc. is standard operating procedure, a game played by the book.
For a million-dollar defense, wouldn’t more innovative defense strategies be expected, or are the tried and true the path to exoneration in this case? Only the jury will determine the outcome.
– Michael, co-editor