The truth is that fiction media (and real cops and prosecutors)
very drastically over-plays the power of facial recognition. It only works when you have two shots of a subject taken from the same angle, under the same lighting conditions, with the same amount of facial hair (or an alternative light source like infrared or radar that can look past facial hair) and so on.
This sort of perfect one-to-one comparison doesn't happen in the real world. Much in the same vein of "enhance that picture for me" doesn't actually happen in reality the way it does on
CSI, "Run facial recognition" doesn't actually work in reality either, unless you're comparing two mugshots.
Even visual unlock facial recognition tools on computers, which rely on you always sitting in front of the computer, under the same lights, and in the same position, have as low as a fifty percent accuracy level, and can be fooled with as little as a cardboard cutout unless they are using differential cameras for comparison (IE 3d-shots)
While you can say certain things about a face mathematically, such as "the distance between the centers of the pupils never change;" the
concept of using facial req as ID falls far short of the
practice and is mostly a psychological fallacy; one of blurry photos and videos, smeared images and off-angles, and cases of "close but not quite" where you have enough points to make a match mathematically possible, but not enough points to guarantee that no other person on Earth, or even in the neighborhood, could have that combination of features.
The same is actually true of fingerprint identification (physical, not DNA) in that, if you're comparing two booking cards, it's possible to make a fairly definitive match, but if you're comparing a booking card to a singular smeared or poorly collected partial taken from a crime scene(the way most people imagine it being done), it's going to be nigh impossible to make a definitive link between the samples, and the best you can say is "it's within the range of possibility that these two are from the same person." with that range being anywhere from 1%-75%.