There are some TV channels that show drammtizations of actual criminal 
investigations. I watched one such story the other day. The detectives 
had surveillance recordings, and they were looking when a break in a 
fence occurred. The started some time after the incident and they went 
backwards day by day by day. It took them 14 iterations. When they found 
the D day they watched the tape for 24 hrs until the incident occurred. 
Things that are self-evident to most of us apparently never occurred to 
the investigators. Lot of taxpayers money could have been saved.