You're not from the US based on your domain name but you're generally free to defend yourself in the US even within SF. > The defendant is not guilty of [whate

You're not from the US based on your domain name but you're generally free to defend yourself in the US even within SF. > The defendant is not guilty of [whatever forceful act was used in self defense] if he/she used force against the other person in lawful self defense or in defense of another. The defendant acted in lawful self defense or defense of another if: > The defendant reasonably believed that (he/she or someone else) was in imminent danger of suffering bodily injury (or was in imminent danger of being touched unlawfully); > The defendant reasonably believed that the immediate use of force was necessary to defend against that danger; AND > The defendant used no more force than was reasonably necessary to defend against that danger In your case with the very real risk of a lifelong perhaps terminal disease from the needle and with that being a biological weapon I DO NOT RECOMMEND but by law you could likely use a deadly weapon in response like a bat/knife/pole/brick in an attempt to prevent you or someone else from being stabbed. I am not a lawyer. On the Street Crisis team front, I imagine they are all able to restrain the guy and that they will be equipped with personal defense such as tasers and mace which will be audited HEAVILY if used.