I'm no lawyer. I don't think you can get a FISA warrant on hearsay. I could be wrong. Might be up to the judges discretion. Might have to ask lindajoy. The big deal in this case (actually asked an attorney) is if the dossier is completely fabricated and or unsubstantiated and there's reason to believe the Investigators knew the investigation is tainted. Any convictions base on such evidence would be "fruit of the poisonous tree" and said convictions would not hold up.
Super Dave wrote:
I didn't say you can't get a warrant with heresay. That was someone else.
They clearly didn't tell the judge they were presenting fake evidence, and he would have no way of knowing it was fake, and it's not in the judges power to get another investigative body to check the evidence to see if it's fake. Again, this is why the issue is so important.
Refer to tip #2 again.