The climax of Trifles features an instance of dramatic irony. Throughout the play, the men continuously belittle the women's concern with "feminine" details, such as the flaws in Minnie's knitting. However, this attention to the remnants of Minnie's activity—particularly those coded as female—ultimately lead the women to uncover the motivation behind the murder. In this case, the dramatic irony at play is produced by the fact that the audience knows something that the men don’t know—namely, that the women have found the key piece of evidence that could be used to convict Minnie and, moreover, that the men have ignored this evidence and written it off as "women's trifles."
The County Attorney says facetiously to Mr. Hale:
“Well, Henry, at least we found out that she was not going to quilt it. She was going to—what is it you call it, ladies?”
The County Attorney's dismissive tone implies that he thinks the women haven't discovered anything of greater importance than the type of quilt Minnie was going to make. However, what he doesn’t realize is that the women are able to use these minor, feminized details to understand the interpersonal dynamics that underpin the gruesome tragedy.
This moment points to the larger irony that infuses all the interactions between the men and the women in the play. While the men think the women are "trifling," the audience observes that they are in fact discovering clues and forming connections that explain the very mystery the men are trying to solve. The men's easy dismissal of the women's thoughts and observations causes them to overlookthe very evidence and explanation they are diligently seeking.