I was thinking along the same lines yesterday.
It is similar to how LE identified the murderer in the Garland case. In that case LE had gone to all the neighbors and residences and businesses and asked them for any home security videos they may have from the day and timeframe of the murder and LE spent long hours looking through them and found a common green truck that appeared nearby the victims home and in other places.
It was amazing. During the trial they ended up with many video clips which showed his truck and the direction he came and went. It was amazing how many times his truck was caught on video from different sources.
The hard part for them was making that first connection which vehicle may have been the perps vehicle but they did it.
With such a small town as Delphi I do really think this approach could work but LE would have had to have asked many residences and businesses for their videos very soon after the murders because most video security systems can tape over the same area as more days are taped.
I hope LE and FBI had considered this at the time. Maybe they have and maybe they are still checking video footage.
http://www.websleuths.com/forums/sh...athan-O-Brien-5-Calgary-30-Jun-2014-29/page35