Snoopy first off I would post the property with a few NO Treepassing signs and ask about the current laws regarding this , here in Missouri criminal tresspassing would cost them hundreds of dollars for each offense .
Next I would do a search for the X10 camera it can be had for $79.99 and it comes equiped to hook up to your VCR with a motion sensor .
Third I would ad a motion sensing flood light or two to the yard .
If the cops refused to do their jobs after a few pictures send the tapes to the local TV news and see if they will run a story on why the cops refuse to do their jobs , and even write a few news papers also .
Mount the camera up high near the guttering to keep them from reaching it and destroying it .
Forget the search here is a link .
http://www.x10.com/products4/overtur...cr_lpdb_2.html
Best of luck hope it works out .