In an example of situational irony, Mrs. Hale and Mrs. Peters are the ones who discover evidence relating to Mrs. Wright’s murder of her husband, not the law enforcement professionals or the one who found the dead man's body. While the three men in the story (the county attorney, sheriff, and Mr. Hale) all believe that they are the ones who will crack the case—and actively mock Mrs. Hale and Mrs. Peters for looking for clues—they are the ones who come up empty-handed.
Meanwhile, the two women find evidence in Mrs. Wright’s quilt that she was anxious and preoccupied about something (as her sewing went astray) and also discover the dead bird hidden in a box, pointing to the fact that Mrs. Wright possibly strangled her husband as a reaction to the fact that he strangled her bird (and, it is implied, was likely violent toward Mrs. Wright as well).
The dramatic irony emerges at the end of the story, when the two women—and readers—are aware of the evidence they found, while the men continue to belittle them for their lack of skill. The dramatic irony increases as the women decide to hide what they found from the men in order to protect Mrs. Wright, while the men continue to believe that the women haven’t “picked out” any “dangerous things.” Here Glaspell is pointing out how oblivious men can be to women’s importance and how the women in the story intentionally use that to their advantage to protect one of their own.
Throughout the story, the men use verbal irony to mock Mrs. Hale and Mrs. Peters for caring about domestic activities and “trifles,” such as Mrs. Wright’s abandoned canning jars and unfinished quilt. The final lines of the story contain one such example of this use of irony:
"Well, Henry," said the county attorney facetiously, "at least we found out that she was not going to quilt it. She was going to—what is it you call it, ladies?" […]
"Knot it," was [Mrs. Hale’s] low reply.
He did not see her eyes.
The verbal irony in this passage—in which George states, "at least we found out that she was not going to quilt it”—is an example of biting sarcasm. George does not actually care how Mrs. Wright was approaching her quilting project, but uses this moment to mock Mrs. Hale and Mrs. Peters for the fact that they cared about such a thing. The fact that “he did not see her eyes” shows how George doesn’t actually care about—or respect—Mrs. Hale's answer and does not see her for the powerful—and equal—person that she is.
Mrs. Hale’s “low” response shows that she does not want to answer his taunting question, but she does so anyway because she’s aware that he is a man with power and, according to the unwritten rules of American society in the early 1910s, she has to respond to him with deference.
