Ah, if the computer containing the CP were in fact at someone else's house then possession is not as clear as one would hope. Courts have repeatedly pointed to "dominion and control" as vital elements to any charge of legal possession.
Without a confession from KZ on the CP possession, they'll likely have a difficult task proving "beyond a reasonable doubt" that he possessed the CP given that he lacked "dominion and control" of the computer containing the CP.
They can/do jump through evidentiary hoops to imply/prove KZ's dominion and control of the computer at a time when the CP was on it and thus possession. But a good (read: well-funded) defense team is likely to be able to parade through a string of computer forensic experts who would poke holes in the prosecution's claims. Password protected computer, digital breadcrumbs, date-time stamps, etc--all of which can be spoofed and compromised. I think that's why LE, despite having long, digital evidentiary trails connecting specific IP's to specific file DL's, often run simultaneous busts on a large number of CP suspects at the same time--so they can catch them in physical possession of the goods
An ancillary consideration is that relative to most of the CP arrests one reads about--where 10's of thousands of files /terabytes of CP are found in a single sicko's possession--KZ's CP collection of 23(?) files barely qualifies as a collection--as offenisve and disgusting a collection as it apparently was.
It's also possible that given the EXTREMELY demented nature of the CP KZ had, that he wasn't necessarily into CP. KZ also apparently had multiple adult GF's?
It's possible that KZ's interest in those specific files was an ephemeral one of a sorta cyber-rubber-necking at a horrific event--like an ********* type interest. Also, the files were found in the default download directory for Limewire. Possibly suggesting he had a one time, disgusting interest that he hopefully didn't follow up on.
No doubt the police and forensic psychiartists and CP experts will be able to determine-- based on other files on KZ's computer/his internet browsing history etc--what KZ's overall/on-going interest in CP was. And given the challenges of proving possession, they might decide to prosecute or not based on their evaluation of why he had those files.
