Legal Question in Civil Rights Law in Missouri

This question has not been resolved as simply as you may want. The problem seems to be how the equipment is used. If the purpose is to deter vandalism, theft and violence, it seems that a notice would be an effectual part of that goal. If the equipment is to view or record guests sunbathing or using the restroom, or through your neighbor's window, the use of the equipment will be later viewed as part of that bad act.

If you just want to find out who has already been doing bad acts like theft, vandalism, etc., then you are probably okay with discrete use of exterior equipment without a sign notifying people that come onto the property. You might also do this inside your home. You should probably avoid bathrooms, guest bedrooms, or anywhere someone might have a reasonable expectation of privacy. If the equipment records, do not share or play it for anyone but the police and your attorney. Perhaps you shoud discuss it with your attorney before letting the police know that a recording exists.

Good luck