GREEN RIVER — The case of Bradley Fairbourn proceeded Friday, although it took a departure from the usual order of things for a science lesson.
Defense expert witness Dr. Greg Hampikian was allowed to testify during what is normally the prosecution’s witness phase.
Hampikian had a scheduling conflict with the normal defense witness phase, scheduled for next week, additionally, expert witnesses from the Wyoming State Crime Lab were available today to hear his testimony and offer an immediate reply.
Hampikian is paid by the defense and also works pro bono in various innocence projects.
He revealed that his fee is capped at $10,000 in the case. He said he takes no opinion on the guilt or innocence of the defendants in his paid work, only reporting the scientific facts. He said his pro bono work in done in cases in which he personally feels the defendant is likely innocent.
Hampikian spoke on the technical aspects of working with DNA samples from multiple sources using probabilistic genotyping.
An example could be a blood stain which came from at least two separate people.
Hampikian explained that in samples with all DNA coming from a single person it is trivial to include or exclude an individual. With two sources, a primary and a secondary source can be found readily by comparing the height of the waves of DNA markers on a graph. The larger source will be replicated evenly at the same rate as a smaller source of DNA.
More than two sources result in statistics, not absolutes, for all but the primary and secondary source. Statistics used to analyze the multi-source sample do not allow an absolute match to a third person, only a probability assigned based on complex mathematics.
Hampikian testified that the software used to analyze the statistics relies on assumptions made by the operator. He explained that by running the software with different starting assumptions, such as the minimum number of contributing people the results can be different.
The odds of an exact match between any two people go down as more markers are analyzed.
The variability comes in because many people might share some DNA markers and the possibility of an additional unknown source can never be ruled out because of the possibility of overlapping markers between the multiple sources.
Hampikian stressed that the ‘amplification portion’ of the DNA testing process results in creating exact, ever compounding copies of the DNA present in the sample.
He explained minuscule amounts, as low as one molecule of DNA will be replicated and could be present from contamination during previous steps in the process.
Previous steps include evidence gathering or lab processing.
Hampikian gave the example of police investigators wearing latex gloves. He explained that the gloves might protect the officer from being contaminated but they don’t protect the evidence from being contaminated by anything that has touched the outside of the gloved hand, including previously handled evidence.
Hampikian used lab experiments involving handling used cups before bagging evidence as an example. He said the experiments reveal that the sensitive nature of modern DNA testing results in easy contamination if investigators fail to change their gloves between bagging each piece of evidence. He explained this contamination is present even as the result of light skin contact with objects. The contact does not need to occur recently, Hampikian said that DNA is very stable unless actively destroyed. He used the example of bleach destroying DNA while alcohol preserves it.
He said past audits have found crime labs where a tech was using alcohol to disinfect an area believing it would destroy DNA. In fact, it preserved the DNA in the lab workspace and resulted in numerous contaminated samples across multiple unrelated cases. This revelation eventually revealed the flawed procedure according Hampikian.
Hampikian’s only detailed criticism of the Wyoming State Crime Lab revolves around the process outlined in paperwork submitted in the Fairbourn case.
Hampikian said that the lab’s paperwork indicates a sample of the defendant’s DNA was present during testing of evidence. He called it “extremely sloppy work” but could offer no opinion on whether any of the samples of DNA, in this case, were contaminated.
He explained that by never having reference samples of a defendant’s DNA present in a lab before the amplification process takes place the chance of lab error is greatly minimized.
The Wyoming State Crime Lab’s witnesses offered their own take on their lab’s process, saying it is FBI accredited and audited. Both internally and externally.
Wyoming State Crime Lab Forensic Scientist and DNA Technical Leader, Christina Buettner testified that the lab follows established FBI guidelines for labs. The FBI standards are considered to be adequate by her to prevent and catch contamination and human error. Although she did concede that a bad actor failing to meet standards or falsifying reports would not always be found out immediately.
The technical breakdown she gave was aimed at explaining how the State Lab maintains their results and highlighted how their procedures differ from the examples given by Dr. Hampikian of procedures at other labs that have resulted in contamination in other cases.
She explained that the lab employs other methods such control samples that would pick up DNA contamination generally if their workflow was conducive to causing it. She said that the controls occasionally catch an issue and the work is redone.
According to Buettner, as a working lab, they must maintain a workflow and caseload for both prosecutors and defense attorneys and rely on their controls and procedures to verify the integrity of the work being done.
She discussed several technical details such as the use of screw top vials instead of flip top that can spray contamination. Along with barcoded samples and robotics used to guard against human error and contamination.
DNA results indicate that Fairbourn’s pants tested positive for blood containing a mixture of Naisha Rae Story’s blood as the primary source, the defendant’s blood, and another person’s blood.
The handle of a knife recovered near the scene tested positive for Fairbourn’s DNA along with victim Linda Mara Natlia Arce’s DNA and one other person’s DNA. The blade tested positive for the blood and the DNA of both victims.
Fairbourn’s shirt tested positive for blood which was found to be solely his own.
The trial continues Monday.