The business deal (Dramatic Irony)
When Wingate and Mr. Borden meet to discuss the fact that Borden will sign away the farm to his brother-in-law, Lizzie listens in, hearing the whole discussion. While they do not know they are being listened to, the audience knows that Lizzie hears about it, which creates dramatic irony.
The hatchet (Dramatic Irony)
When Lizzie first comes into the room with the hand hatchet and the message for her stepmother, Mrs. Borden, we know she is holding the hand hatchet, but Mrs. Borden does not. This is a tense moment of dramatic irony, in which we can infer that Lizzie is about to kill Mrs. Borden, but Mrs. Borden has no idea.
Mr. Borden comes home (Situational Irony)
Just as Lizzie and Bridget are hatching a plan to get away with the murder of Mrs. Borden, Mr. Borden arrives home early. It is not part of Lizzie's plan to have to kill her father, but in this moment, she must kill him, a man whom she loves dearly, in order to prevent him from finding out about the murder of Mrs. Borden.
Mrs. Borden is dead (Dramatic Irony)
When Mr. Borden arrives home early, there is a great deal of tension and suspense stemming from the dramatic irony that he does not know that Lizzie just killed Mrs. Borden, his wife. While the audience knows about the grisly murder, he has no idea.
