Punish the category of crime aggressively & severely enough, and evidence of such crimes will be hard to come by. Include lewd abuse of that evidence in the scope of "libel", and the occurrence of such crime can be reduced further.

A key problem which this solves, and which is a terrible side-effect of such law as currently implemented, is crushing punishment of those oblivious to their possession of such content (say, malware surreptitiously caches such content on your computer, then anonymously sics CSI SVU et al on you).