Has 'fruit of the poisonous tree' ever shut down a line of evidence in a terrorism investigation? Will it? I don't really expect our security apparatus would

Has 'fruit of the poisonous tree' ever shut down a line of evidence in a terrorism investigation? Will it? I don't really expect our security apparatus would tolerate a restriction like that. 9/11 changed everything... If they can't get their way in the courts, who takes the fall for "letting a terrorist go free"?