tends to speculation , conspiracy theories or , at best , circumstantial evidence 
(ROOT (S (VP (VBZ tends) (PP (IN to) (NP (NP (NN speculation)) (, ,) (NP (NN conspiracy) (NNS theories)) (CC or) (, ,) (ADVP (IN at) (JJS best)) (, ,) (NP (JJ circumstantial) (NN evidence)))))))
(ROOT (S (VP (VBZ ) (PP (IN ) (NP (NP (NN )) (, ) (NP (NN ) (NNS )) (CC ) (, ) (ADVP (IN ) (JJS )) (, ) (NP (JJ ) (NN )))))))