Pretty much everything in forensic science turns out to be junk science over a long enough timeline. Hair, bite marks, fire progression, all junk. There's even a few cracks in the fingerprint wall. Don't get me started on all the field test kits of various types that LEOs use.
The only things that seem to be reliable are things that don't have their roots in forensic science (e.g. using DNA to identify people) and even then you still have to depend on a crime lab (run by the people doing the prosecuting) to not be sloppy.
>crime lab (run by the people doing the prosecuting) to not be sloppy
Oh yeah. Not just incompetence, but actual malice. Recently in Massachusetts there were two high profile state forensic drug lab scandals: One where a chemist was functionally incapacitated by taking all the drugs she should have been testing [0], and one where the chemist was falsifying positive tests (!!!!!!) [1]. More recently, the state police are known to be falsifying overtime records [2]. I can't even begin to imagine what it's like in "stereotyped as corrupt" states.
This has had the opposite effect of what you seem to be implying. It's something that's come up quite frequently in discussions of jury nullification [1]. Jury nullification being when a jury ends up voting not guilty, even when they believe the defendant guilty, generally because they do not find the law (or possibly the punishment) just.
For decades a rate of about 5% for hung juries was typical. In more recent years some jurisdictions have seen more than 20% of cases end in hung juries. [2] Some have seen this as evidence of a rise in jury nullification, but others have argued that it's due to the 'CSI Effect' [3] with these individuals believing that, because of shows like CSI, the standard of proof required for a conviction seems to be rising - along with a reduced weighting given to things like circumstantial evidence.
High quality video can be quite useful for getting closer to the truth in many cases. Fits under your tech not developed for forensic science category though.
The problem with the DNA tests we use today, assuming even perfect cases with zero contamination or mistakes (whole other argument there), is that (in my non-expert understanding):
* Taking the samples and using several solutions to snip them at given patterns.
* Taking another solution and promoting replication of the fragments.
* Using some dye and a weight sorting channel to bin the fragments by weight.
This results in a kind of 'bar code' that graphs the distribution of weights as a VERY crude hash of samples of DNA.
It's pretty useful for determining things like IF it is LIKELY that individuals are related.
It's also pretty good at confirming negatives (We're sure someone is NOT related to X).
It's not that great at confirming positives. That is, the results are both subjective and ambiguous given the hashing. A "positive" result here is really more of an "OK, it's likely we should run the real and expensive check, evaluate if someone might be a suspect by other merits, etc."
I would, offhand, consider a "positive" above to be enough evidence to produce /suspicion/ and /warrants/ to locate other specific evidence to ascertain an actual guilt or innocence based on harder evidence. If an actual "sequence the whole set of samples" option enters the realm of feasible tests then it would also warrant actually doing that.
Come to think of it, I'm not sure how the Ancestry/etc novelty DNA tests work. I'd assume they've isolated a few specific markers they're looking for and the processes are optimized towards identifying those and comparing combinations for those specific traits.
You’ve described electrophoresis DNA fingerprinting correctly, then jumped to the unjustified conclusion that it’s a VERY crude hash.
Not so, it’s a fairly excellent hash, one with few collisions. Better than a fingerprint. If it looks like your DNA, it most likely is.
Source: was an electrophoresis tech (not forensic) in a previous life.
And yes, the usual genetics sites do SNP tests, which are cheaper than full sequencing but mean that they only find what they’re already looking for.
The price of full sequencing is dropping rapidly, I look forward to it being a standard part of medical practice, it will save a lot of lives and improve quality of care.
DNA tests prove a very specific narrow fact, and it’s up to lawyers to string together a hypothesis in order for it to have relevance.
Unfortunately all too often the DNA test result is used as proof of a hypothesis, not of the mere presence of surprisingly similar DNA in a swab sample.
Apropos of this, but about human incompetency rather than DNA tests, the Phantom of Heilbronn. A serial killer so well concealed that her very existence was only given away by DNA traces.
Yes it does, good reading skills. That's the point. Human incompetency, related to DNA forensics.
I didn't outright say that, though; the idea was that I would prepare you for a story of a serial killer so well concealed that her existence could only be inferred from trace DNA, but THEN there's the surprise twist - there is no serial killer, it's a trick of human incompetency. BOOM!
The twist has a much greater effect because I didn't give it away at the start, but the twist also ties back in to my original statement about human incompetency - but NOT where you may have been expecting, and subverted expectations are a key part of surprise twists - and the story is also about DNA forensics. That's the previous subject again, the reader having been led around in an interesting and surprising circle.
Pretty much everything in forensic science turns out to be junk science over a long enough timeline. Hair, bite marks, fire progression, all junk. There's even a few cracks in the fingerprint wall. Don't get me started on all the field test kits of various types that LEOs use.
The only things that seem to be reliable are things that don't have their roots in forensic science (e.g. using DNA to identify people) and even then you still have to depend on a crime lab (run by the people doing the prosecuting) to not be sloppy.