we hunters are our own worst enemy. you have good ethical hunters and bad unethical hunters. i've had a neighbor like this in the past. he knew where the line was and we had just cut our timber. he was hunting our cutover. unless the GW or you see him take a deer on your place or you catch him physically on your property you have no recourse. if your problem hunter does in fact know where the line is then he or she is an unethical hunter and is doing more to give hunting as a whole a bad name. as far as catching him, good luck. crimes are committed every day by people who have "motive" but without evidence you have no case.