The chance to get two almost identical pictures is rather small. I am tired and don't want to calculate, but even if you assume each stain is either "black" or "white", you can say the probability is p=0.5 for it to be white or black. Now you have 8 or so columns it the picture. The chance to get two identical ones would be 0.5^8 for 8 columns, that's around 0.004, so 4 in thousand. Correct me if i'm wrong, i'm tired and would better sleep now. Sure, in such a lab you probably do have thousands of pictures, i guess that's true. But still, it's not as if you get identical pictures all the time.
Now usually you name pictures according to the date when they were taken or in some other way that will allow you to identify them.
Why would they end up in the same folder?
I'm not saying there was "fraud". That term might be wrong here anyway. Maybe better say "doctored" or something like that. But like i said, at least in my mind, this need an explanation.
Edit: One argument against a "fraud" would be that it would be really stupid to use a picture you have already used in an article or something like that...
Either way, that was only my assessment, and i did not say i know what happened here. Just that it raises questions for me. Sorry if that disturbed anyone. But i'm really tired of the BS no matter what side it comes from. I want answers for this disease and we will only get them once the BS stops, we stick together, get organised, make good plans and pursue those plans.