Guess you'll have to check your local laws, as everywhere has their own local stuff. The only experience I have personally with "yard traps" was an old lady down the way lived on the parade route in New Orleans and people were always urinating in her yard. She told the police several times, but they told her that the crowd was too big, her flowers were not high priority, she could NOT have an officer placed by her yard to guard the flowerbeds from pee. So, she ran electric wire along the property, and a couple drunks got a little shock when they urinated in her yard. The police were called to her home, and they made her take the wire down.....but they did put an officer there (since they had to have them along the parade route anyway). As far as someone suing you: remember the big story that made headlines everywhere from a million years ago, when someone broke someone's house, got stuck in the garage and couldn't get out, had to eat dog food until the family returned from a trip and he successfully sued? Or that time when someone was trying to break in and hurt himself, and sued. So, I would guess that unless things in the system got fixed since then, yeah you could probably get in trouble if someone was hurt. Motion sensory lights, video cameras, a yappy dog would be the direction I'd go if you had an issue. Once, police were doing surveillance on my mom's neighbors (drug dealers). They were hiding, we didn't know it but we had suspicions of "something" and went to the police several times (footprints in the garden, trampled flowers, a noise in the night, etc). The police never told us anything. Then one day a policeman saw someone trying to break into the neighbor's (drug) house with a gun and took off running, tried to cut across our backyard. But in the dark he didn't see some pots and a fence and he crashed into it, and mom's 7 dogs come tearing out of the back porch where they slept all at once barking up a storm. We heard a loud expletive yelled under the window where we were watching tv, dogs going crazy, and my brother stepped outside with a gun. The police came to us and our OTHER neighbors the next morning to tell us what was up (so we didn't shoot a cop?)----the man had terrified us, since we didn't know he was creeping around our yard in the middle of the night. At least then we knew to ignore the strange "quiet" noises and the drug house was busted and everyone jailed shortly after, thank goodness!!!