Bite mark identification was used forever until blown up by particularly shameless grifting, and has never been shown to work as practiced. [1]

Tennessee still uses dowsing rods. [2]

Fingerprinting as practiced is a bundle of folk practice, guesses, and some science. Quality varies wildly. [3]

Fiber analysis, lie detectors, spatter analysis and many more techniques are all crap. When one bogus method is finally found legally unreliable, cops and prosecutors find a new one.

[1] https://innocenceproject.olemiss.edu/radley-balko-reports-on...

[2] https://www.themarshallproject.org/2022/03/17/witching-dowsi...

[3] https://www.aaas.org/resources/latent-fingerprint-examinatio...

And I'm wondering about that, because we know the criminal must have been a pretty hard-core cryptocurrency nut. There aren't THAT many of them in Norway (they've already concluded they are a fluent Norwegian speaker).

Instead of facing it just as a lead, it might influence investigators to, consciously or not, build confidence in framing a (wrong) person and and end up building a compelling case against them.

The person who wrote the ransom they believe to be fluent in Norwegian, there could easily be other people involved who're foreign.

Do we?

I was still under the impression everybody was blaming her husband for the disappearance.

As for malicious actors, wouldn't that be a risk for most forms of evidence? Likewise, wouldn't many of the techniques used to establish the validity of other forms of physical evidence be applicable when these techniques are used?