I've sometimes wondered about that when I hear people being charged with something that's 100% digital evidence, it's concerning.
People are innocent until proven guilty. And unfortunately, I'm sure there is that 1% who are still innocent even after being convicted..
I also note that the term 'child' means vastly different things in different contexts and to different people.
Theoretically it would be possible to have the intention of downloading/watching pure porn, and not realize that underage's had gotten caught up in the mix of it. Thus the evidence would be very solid, except that little piece of evidence missing that you knew they were underage....
Especially relevant if/when the context is, i.e.,. 17 yr olds. I.E. some people call Epstein's saga a matter of "child porn", and still others call him (incorrectly) a pedophile, when that's not really what the word means. Personally I'd prefer the terms not be so malleable, because if someone really is into 5 year olds that's something I'd put in a whole different category than 16-17 yr olds, it's just an entirely different thing. They both may be wrong (the latter only in the last 1% of human history), but they are entirely different.
But I digress..