Bland slips up when he states it is to  enable him to proceed on his path to the murder of Duncan. 
( Bland ( ( ( slips up ) ( when ( he ( states ( it ( is ( to ( enable ( him ( to ( ( proceed ( on ( his path ) ) ) ( to ( ( the murder ) ( of Duncan ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Bland)) (VP (VBZ slips) (PRT (RP up)) (SBAR (WHADVP (WRB when)) (S (NP (PRP he)) (VP (VBZ states) (SBAR (S (NP (PRP it)) (VP (VBZ is) (S (VP (TO to) (VP (VB enable) (S (NP (PRP him)) (VP (TO to) (VP (VB proceed) (PP (IN on) (NP (PRP$ his) (NN path))) (PP (TO to) (NP (NP (DT the) (NN murder)) (PP (IN of) (NP (NNP Duncan)))))))))))))))))) (. .)))
It is not clear whether or not Bland murdered Duncan.
( It ( ( ( is not ) ( clear ( whether ( or ( not ( Bland ( murdered Duncan ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (RB not) (ADJP (JJ clear) (SBAR (IN whether) (FRAG (CC or) (RB not) (NP (NNP Bland) (NNP murdered) (NNP Duncan)))))) (. .)))