Proof consumer put files there (Score 1)

My question is, where is the proof that the files were even put there by the consumer? What is stopping a techie who, say, doesn't like the guy or is feeling particularly vindicative, from 'planting' supposed pornographic images and then calling the cops? The police should definitely have gotten a warrant, and then, of course, there'd have to be the proof that the files were put there by the owner of the PC. You could argue that once your PC left your possession, you have no control over what is on it.