In most places in the US, someone who is on your property without invitation and without otherwise being permitted by law (police, fire, mail carriers, delivery people) or prior agreement (condo personnel, lawn care, etc.) has no standing to sue for injuries received on your property.
The vast majority of "I slipped on your sidewalk" type lawsuits are
*illegal* nuisance suits that *should* result in judicial fines for the person who sues and for their lawyer (if any) who should have known better than to file the suit in the first place.Unfortunately you need a judge willing to sanction the nuisance (and most are not). The majority of nuisance suits are dismissed without prejudice, which means that the people who file them have no record and so are free to do it again.
George