So, on one side I am glad that you are going to install security cameras, but there are several questions:
1) Why did you wait so long to install them? This is something that made sense to do since day 1, no?>
2) What is the intent? You catch them breaking the lock, then what? Arrest them for breaking and entering? Use that in court? I am sure they agree that they go to the site periodically but they are going to claim that is their property...so what does videotaping get you? These guys are not going to pay you, so is this just evidence gathering for litigation?
