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)))))))))))))))))) (. .)))
Bland makes an error by acknowledging his intent to follow his path to the murder of Duncan.
( Bland ( ( ( makes ( an error ) ) ( by ( acknowledging ( his ( intent ( to ( ( follow ( his path ) ) ( to ( ( the murder ) ( of Duncan ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Bland)) (VP (VBZ makes) (NP (DT an) (NN error)) (PP (IN by) (S (VP (VBG acknowledging) (NP (PRP$ his) (NN intent) (S (VP (TO to) (VP (VB follow) (NP (PRP$ his) (NN path)) (PP (TO to) (NP (NP (DT the) (NN murder)) (PP (IN of) (NP (NNP Duncan))))))))))))) (. .)))