Everybody is familiar with the flood of "forensic crime" procedural TV shows saturating the airwaves in the early 2000s.
Fascinating nerds would look at physical evidence from a crime scene and figure out everything that happened and who did it.
Viewers at home are amazed seeing that crime has been conquered by science, and many people subsequently actually devote themselves to becoming "forensic criminologists".
The disappointing thing is that this forensic thing is really a lot of made up bullshit with almost no actual explanatory or scientific validity.
It turns out that there is really no established, agreed upon criminal forensics, no standards, no schools, no common practices.
It really seems like they're consulting hard scientific principles, when in fact they're pulling it out of their asses.
Not rigorously trained professionals based in hard science, but clever science geeks making shit up based on hunches of what they think "should" be true, using individual techniques and coming up with mostly unrepeatable results that don't match up with anybody else.
Kind of like medieval barbers, only not as organized.
From watching this stuff you come to one major conclusion: the results are such that any scientist given the same evidence would come to the same conclusion.
Nope.
Case in point: several decades ago, an old lady was found dead, clearly murdered, with little evidence besides a distinct human bite mark on her body.
The detectives went crazy trying to find a perp, and finally they matched the activities of a local young guy to the timeline, and picked him up.
They brought in a "bite mark expert", a forensic dentist, to match the teeth of the suspect to the marks on the victim.
What do you know, a perfect match!
(Fwiw, the victim was white, and the suspect was black.)
Kid gets sent away to prison for decades, all the time whining, "i didn't do it".
His lawyer keeps petitioning, but the years go by.
Finally they manage to revive the case to re-examine the validity of the bite marks.
We all hear about how victims of horrible accidents can be identified by their dental records even when nothing else remains of them, so we think DENTAL RECORDS are special, a "gold standard", like fingerprints.
They might be, but actually taking the prints and matching them is a whole nother deal.
These are complex 4D mechanisms working on each other, the teeth in the mouth of a person who is moving making marks on the 4D tissue of another person who is moving in time.
Depending on the angles and relative positions, which are actually in motion, almost any marks could be made.
It's almost unimaginably far from pressing an inked finger down onto a piece of paper.
Add to that the marks in organic human tissue aren't stable, they change as the tissue degrades.
But shouldn't there be a way to match teeth with the bite they produce?
Sure, but there are many more ways to fuck it up than there are to get a reliable match.
And there is NO RECOGNIZED ESTABLISHED PROCESS for doing this, you have to rely on anyone who says they can do it, and take their word for it.
"So you can remove my brain tumor? Do you have a diploma?"
"Nah, but I've been doing this for years, you'll be alright."
Anyway, they revisited the technique the forensic dentist used to match the teeth with the bite, and found out it was absolutely insanely variable.
Might as well glue some teeth to a strap and beat a piece of pot roast with it until you say, "Aha! We've got it!"
Looking into it you find no standards for how to match teeth to any kind of marks. As it turns out, matching a person to a given bite injury is almost ludicrously unreliable.
After like 3 decades in prison, this guy is finally released.
There are some forensic techniques that are reliable, like DNA. It's not done at all like you think it is, and they usually narrow suspects down to a family before selecting the likely individual.
But DNA science has very good odds.
"Bones", "NCIS", etc, not so much.