Unless she subsequently got your friend's ID card, phone number, or address, there really isn't any way for a random stranger to sue you for something that randomly happens on some random street. This isn't like doing CPR on someone without your First Aid Graduate card and getting sued because you accidentally broke a few of their ribs while saving their life. Even then, your friend could have given up his handkerchief and acquired a new one. Or you could simply accept that, since he didn't have disposable tissue on him, he did not have to feel obligated to relinquish his personal handkerchief.
Let me put it this way: if this strange unknown woman somehow gave your friend a disease then went around to finding exactly who he was and pressuring to sue him for giving it to her, she still would have little ground for Just Cause due to the random elements involved. She would have to have proof that previous blood tests during her annual doctor visits showed that she was negative of such a disease (and if she didn't see the doctor at all prior, there would be no grounds to sue) prior to her encounter with your friend. Your friend would have to show similar, which is why I highly recommend everyone sees a doctor for a harmless checkup once a year. Even if the evidence (the tissue) were proven to be infected, it could not be used as evidence unless there was followup proof that one of you had the disease previous to the tissue incident. And even then it could be dismissible due to 'other factors' that would have caused the disease, which a lawyer with any sense would bring up.
This is leaving out the fact that you need money in order to hire a lawyer and file a lawsuit. A homeless person would not.
Yes, the dumbest lawsuits in the world happen, but commonsense and a little knowledge on legalities can go a long way.
Let me put it this way: if this strange unknown woman somehow gave your friend a disease then went around to finding exactly who he was and pressuring to sue him for giving it to her, she still would have little ground for Just Cause due to the random elements involved. She would have to have proof that previous blood tests during her annual doctor visits showed that she was negative of such a disease (and if she didn't see the doctor at all prior, there would be no grounds to sue) prior to her encounter with your friend. Your friend would have to show similar, which is why I highly recommend everyone sees a doctor for a harmless checkup once a year. Even if the evidence (the tissue) were proven to be infected, it could not be used as evidence unless there was followup proof that one of you had the disease previous to the tissue incident. And even then it could be dismissible due to 'other factors' that would have caused the disease, which a lawyer with any sense would bring up.
This is leaving out the fact that you need money in order to hire a lawyer and file a lawsuit. A homeless person would not.
Yes, the dumbest lawsuits in the world happen, but commonsense and a little knowledge on legalities can go a long way.