speculation , conspiracy theories or , at best , circumstantial evidence 
(ROOT (NP (NP (NN speculation)) (, ,) (NP (NN conspiracy) (NNS theories)) (CC or) (, ,) (ADVP (IN at) (JJS best)) (, ,) (NP (JJ circumstantial) (NN evidence))))
(ROOT (NP (NP (NN )) (, ) (NP (NN ) (NNS )) (CC ) (, ) (ADVP (IN ) (JJS )) (, ) (NP (JJ ) (NN ))))