stetson said:
They may have collected security video but I will be very surprised if any of it predates the murders. I think these videos are used for more immediate events such as robberies and not kept.
All security cameras I have used over the last 20 years have been connected to a Digital Video Recorder and the ones I use hold the files for 90 days before purging for storage. If he was already a suspect by early December they would likely be able to find him on any visit from middle of September to the murder date.
I imagine it would be simple to track the dates because most everyone pays with a credit or debit card. I have no doubt cops have reviewed all of his credit and banking charges, unless he always paid cash it would be easy to get the video.
I suspect they also tracked the purchases of the items he bought at WalMart through his credit cards.