There is an joke in the criminal defense bar….
Q: What does forensic firearm and toolmark analysis have in common with interpretive dance?
A: They are both totally subjective with no universal or applied method to determine the quality of the results.
Why: You see when it comes to this form of pattern recognition, meaning forensic firearm and toolmark analysis, there are no points of comparison that are used or any clearly applied universal agreement among even the most practiced and ardent believers of this form of forensic science.
Instead, often non-credentialed lay witnesses who were former traffic cops who are trained by others similarly lacking in an engineering or tribology background using a quasi-apprenticeship method, make the call of a “match”. The term of art (or the call meaning the use of the word “match”) used by these practitioners is arrived at by these untrained microscopist looking with what amounts to their “highly trained set of eyeballs” at a three-dimensional object under a insufficiently magnified stereo comparison microscope which is a two dimensional representation to arrive at the conclusion that there is supposedly “sufficient consecutively matching striae” to warrant a conclusion that the unknown and the known are in fact a match.
The way they are trained is that they twist and turn and try to orient (not unlike dancing) the known and the unknown until they think it lines all up, but all is done without using any sort of matching criteria such as a number of points of comparison between the objects, until like manna from heaven the answer reveals itself.
The kicker of it is that oftentimes photomicrographs are not taken that would allow for external review and verification. So you end up with a “trust me, I’m from the government I am here to do no harm” situation.
Bet you cannot say that 5 times fast. That is the conclusion, let’s unpack and define the concepts.
- Points of comparison-a methodology wherein similarities between two samples are looked for to try to find
- Tribology-is the study of the unequal and equal application of force upon interacting surfaces in motion. Basically wear, friction and lubrication.
- Stereo or comparison microscope-it is a type of microscope whose optical bench is set up in such a way that two images are set side-by-side creating a split view window allowing the two objects to be viewed at the same time side-by-side.
- phtotomicrographs-photographs that can be taken through the microscope to record more or less what the observer of the compariosn microscope sees.
- “Sufficient consecutively matching striae”-beats me and the rest of the scientific world has no clue either
Let’s leave funny interpretive dance to YouTube. In the courtroom let’s demand facts and empiricism.