Putting fingers on the keyboard

Hi all,

I am currently working on a piece of work for uni. The aim is to see if there are any inappropriate images on the PC.

I can see that the images were indeed under the case suspect (owner SID same as user, and was stored under their user profile. They have come up in encase as lost/recovered files.)

My question is - how could I prove that the user in question actually put the pictures on the machine? The user account did not have a password, so someone else could have easily done this. How is this dealt with in industry? What would happen if you have found indecent pictures, but you cannot prove that said person put them on the PCs. Is evidence being on a machine enough to stand in court?

Thanks
kirby-11