In "Macbeth" king Duncan is physically murdered in act 2 scenes 1-2 by the Thane of Cawdor, Macbeth, he is unable to be held completely responsible for the murder as many other characters can be held responsible for motivating him to do the deed. The main suspects are: the three witches, Lady Macbeth, Macbeth himself, Duncan and the guards. So far in the play Macbeth has become the Thane of Cawdor by winning the battle against the Norwegians and Macdonald. Then Macbeth returns home where he reunites with Lady Macbeth and she persuades him to kill Duncan which he then does. .
To most people the witches are the primary suspects for forcing Macbeth into killing king Duncan, this is because it is thought that the witches first put the idea of killing Duncan into Macbeth's head although this is not the case in my view. Before the battle the witches plan to meet Macbeth and they do not talk of Macbeth and the king a lot. When Macbeth arrives he and Banquo question each other on the witches appearance and it is evident that Banquo suggests the witches are able to understand what he was saying when he suggests," You seem to understand me." This first puts the idea into Macbeth's mind that the witches can speak, he then says," Speak if you can: what are you." Here, Macbeth is anxious to see what the witches are going to say because the witches were hesitant to say anything to Macbeth and Banquo before. I believe that the witches weren't going to say anything about Macbeth and power until Macbeth persuaded them, so basically it was Macbeth's own fault for making the witches say what they said. Although other arguments could be that the witches knew that Macbeth was going to ask of their speech because they could predict the future, but Shakespeare made no reference to the witches predicting that Macbeth would ask for them to speak. Then they speak in act 2, scene 3, lines 46-48, .
"All hail Macbeth, hail to thee, Thane of Glamis .