Macduff immediately suspects Macbeth of being guilty of Duncan's murder. ... And Macduff articulates his suspicions by asking Macbeth why he killed Duncan's guards, the men largely believed to be responsible for the murder.

How is Macduff suspicious of Macbeth?

Macduff is more suspicious of Macbeth than any of the others because he was with Macbeth and observed his guilty behavior. He hates Macbeth for killing the king, and Macbeth hates and fears Macduff because he knows Macduff knows he is the guilty party.

What characters suspect that Macbeth murdered Duncan?

Banquo suspects that Macbeth killed Duncan in order to become king. Macbeth invites Banquo to a feast that night.