When the detectives eat the leg of lamb in “Lamb to the Slaughter,” it is an example of situational irony. You might think that this is dramatic irony, but it is better to say that it is situational.

Dramatic irony occurs when we, as the audience, know something important that the characters do not.  This would seem to be what is happening when the detectives eat the lamb.  We know they are destroying the murder weapon (the only evidence that can point to Mary Maloney’s guilt), but they do not.  However, dramatic irony is supposed to cause suspense that will later be resolved.  That is not the case here because the scene in which the detectives eat the leg of lamb is the end of the story.  Therefore, it does not build any suspense that gets resolved.

Instead, this is situational irony.  Situational irony is when there is a big difference between what you expect to happen and what does happen.  In this story, we would expect the detectives to be smart and able to uncover any clues that will point to Patrick Maloney’s killer. We expect them to find and arrest the killer. Instead, what we get is the detectives destroying the evidence.  Instead of finding and arresting the killer, they make sure that she will never be caught.  This is situational irony because it is very different from what we expect.  It is more like a joke and less like something that is meant (as dramatic irony is) to build suspense.