What is scientific testimony?
The Star Telegram had an article addressing the debate over the use of forensic testimony in criminal cases. They had the audacity to point out the conclusion of the National Academy of Sciences report that ballistics is not science - it's an opinion. Of course, that drew responses from crime labs, and those who regularly testify on such matters. The point of the article was not to answer the question of whether it's science or not, but point out the issues are currently being debated. In Texas, these type of issues were supposed to be addressed by the Texas forensic Science Commission.
Lawyers are known (despised) for arguing over words - yet we don't challenge the use of the term "science". So what is the definition? Here's one:
The word science comes from the Latin "scientia," meaning knowledge.
How do we define science? According to Webster's New Collegiate Dictionary, the definition of science is "knowledge attained through study or practice," or "knowledge covering general truths of the operation of general laws, esp. as obtained and tested through scientific method [and] concerned with the physical world."
As far as I'm concerned, a crticical part of science is utilization of the scientific method. What does that mean? While its been a long time since I was in school, it basically means formulating a hypothesis, and then testing to see if its true. Rigorous testing means attempting to disprove the hypothesis. If you can't disprove it, then it's probably scientific.
So how does this apply to fields such as ballistics, fingerprints and blood spatter? I don't think it does. The underlying assumptions for those disciplines has never been established: i.e. there are no studies establishing that no two fingerprints are the same, or guns put the same marks on bullets to the exclusion of all other guns. Ultimately, all those fields are based on one thing - observation.
The problem with observation is that no matter what procedures you follow, the ultimate decision is subjective.That is the problem with those fields; if something is true, everyone that looks at it should reach the same conclusions. If you have two equally qualified experts reaching different conclusions, that's not scientific.
Another problem is determing who is an expert. Is it someone who looks at a lot of fingerprints or ballistics. Does that mean they are able to accurately look at something at make comparisons. Why don't we use artists - who have a discerning eye for detail? Also, if it's nothing more than making comparisons, why do you need an expert?
We need to start addressing this type of testimony for what it is - opinion. What's the answer? I don't know. Perhaps its the use of court experts, or perhaps its in limiting the use of such testimony, or providing limiting instructions. Something needs to be done, because there is no doubt that as long as you have competing opinions one of them is likely to be wrong - and it is justly likely to be the state's expert as the defense expert.
