They'd have to be looking at a person's hard drive for a specific reason and with a warrant, like If the person was on the e-mail distribution list of a child pornographer.
Prosecutors who do this stuff are good at it- a poker buddy of mine is a Federal prosecutor who goes after child pornographers. The point he made to me is that they never find someone with just one picture or video- when they find this type of stuff after executing a search warrant, they find hundreds, if not thousands, of videos and pictures. It's tough to argue that you did not receive the stuff intentionally.
The worst is that they'll see the same child victim in pictures and videos over the course of years from a very young age to their teen years, in some cases. They just don't have any way to track the kid down. They can arrest the guys with pictures of the kids, but they can't find the victims.
If a guy is in the practice of collecting those kinds of pictures, then I can see that he would have a whole bunch of them. But, in some Free Republic articles (I don’t know..., around a month or two ago...) there was mentioned some guy who had a computer in for repair and the technician spotted a picture on his hard drive. The police were called and they looked through the drive and found something like six or seven of them. So, the guy was prosecuted.
I guess someone could say he didn’t have time to collect as many as he wanted to... LOL... but, at the same time, perhaps there are those who have one or two or five or six, etc.
Then again, there is the issue about family pictures (that I mentioned in an earlier posting). I’m not sure where they draw the line, because certain pictures are okay, while others are not. I guess it would be easy enough to prove whether someone was in the family (for family pictures), but..., it’s okay for people to even have strangers’ pictures of things like family nudist places or even some printed material by certain professional photographers that put it out for art.
I don’t think there should be problems for families and their own personal photos, as I remember the day, a long many years ago, when people did have photos of little kids running around without anything on, and they would all laugh about it... :-)
Nowadays, it seems to be very dangerous for even stupid little things like that.