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.

1. Points of comparison-a method­ol­ogy wherein sim­i­lar­i­ties between two sam­ples are looked for to try to find
2. Tribology-is the study of the unequal and equal appli­ca­tion of force upon inter­act­ing sur­faces in motion.  Basi­cally wear, fric­tion and lubrication.
3. 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.
4. phtotomicrographs-photographs that can be taken through the micro­scope to record more or less what the observer of the com­par­iosn micro­scope sees.
5. “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.