strolls through this mess with a smug grin , 
(ROOT (S (VP (VBZ strolls) (PP (IN through) (NP (DT this) (NN mess))) (PP (IN with) (NP (DT a) (JJ smug) (NN grin)))) (, ,)))
(ROOT (S (VP (VBZ ) (PP (IN ) (NP (DT ) (NN ))) (PP (IN ) (NP (DT ) (JJ ) (NN )))) (, )))