This is why:

- the whole roll of negatives was prime evidence;

- police forces were one of the biggest users of Polaroid instant film.

And moreover, who had a darkroom and the skills to edit substantially a picture?

Whereas here we have nobodies being able to generate pixel-perfect fake "evidence" from the computers they already have.

Plenty of people. If you have running water, some tape, and trashbags, you too could have a darkroom.

https://www.metmuseum.org/exhibitions/objects/objects@exhibi...

The roll itself can be manipulated too. Most of the techniques used in modern photoshop are basically 1:1 carry overs of darkroom processes. Layers, dodge and burn, masking, etc.

There was a time you could take this class in highschool.