"was the man spying, or did he think that he was spying?" "was he spying for israel, or did he think he was spying for israel?" Yes, this is a problem. Spy rings from all over the world go to US Jews and tell them they are the Mossad and need help. And if the americans believe them and help them out, they have no possible way to tell who they are actually spying for. So if Mossad does ask you to provide them with information, for gods sake call the Israel Embassy and ask them to confirm that it's really Mossad and not KGB or KCIA or, well, anybody.
High school teacher's union threatens strike (Haaretz)
from the article: U.S. Jew indicted as possible Israel spy