Calling the police to report the trespasser(s) would be an appropriate response against a trespasser. In Arizona, trespassing is a serious crime and it is not looked upon lightly. Charges range from a class 1 misdemeanor to a class 6 felony depending on the type of criminal trespass. (A.R.S. § 13-1501 through 1504). However, to be convicted of this crime like any crime, there must be criminal intent. Therefore, if it could be shown that one was merely passing through a neighbor's yard without the intent to commit a crime, then there would be no consequences.

On the other hand, ignorance of the law is never an excuse because one should know better than to trample through someone's yard without their permission.

There is another important factor to consider.  What happens if that trespasser gets injured while on your property? Would he or she be able to sue your mom? And would you be insured for the damages under your Homeowners policy? This answer takes some explanation and you may want to consult a local attorney.

Today a trespasser who gets hurt on your property can sue you, if you have permitted a dangerous condition to continue. Whether the fence you constructed is considered a dangerous condition is something you should discuss with an attorney or the city officials where you reside. Contacting your City or an attorney will help guide you on reasonable steps to take.  Additionally, if you have a homeowners' policy, you should contact them as well.