Federal reserve notes have serial numbers, which may be recorded when placed into an ATM. Perhaps they then look at which bills with withdrawn by which account and/or retrieve ATM video footage. Or maybe I've been watching too many police shows.
recording a small serial number from a blurry, black and white, 480*360 camera? good luck.
No, I meant that the bank may record which bills were placed into which machine. Then, the police do a reverse lookup on the serial number, finding the bank. The bank then tells police which ATM they were last placed in and the police watch the video camera footage from the ATM to see who makes withdrawals. I think I actually saw this on Castle, so I'm not sure if it's viable or not.