Each photo in possession is a separate crime and they, presumably, know about and want a single photo. However different legal doctrines say, if they find more in the normal course of events, they are now admissible and can be used to create new charges.
> However different legal doctrines say, if they find more in the normal course of events, they are now admissible and can be used to create new charges.
Sure, but that's not the case here. They apparently already know he possesses a certain number of such photos, and now are now trying to compel him to incriminate himself further.
