A big theme in "Trifles" is the illustration of traditional gender roles. The men in the play display personalities of purpose and analytical skills in conducting their investigation. The men belittle the women, insisting on man's role as public figure and woman's role in the home. Historically, this public/private dichotomy has been used to instill and sustain the idea that men work in the external world and a woman's place is in the privacy of the home. For example, near the end of the play, Mrs. Peters sarcastically acknowledges that the men would laugh at their evidence and any suggestion that it (evidence) might lead to a conclusion about the crime:
My, it's a good thing the men couldn't hear us. Wouldn't they just laugh! Getting all stirred up over a little thing like a--dead canary. As if that could have anything to do with--with--wouldn't they laugh!
Of course, the dead canary had everything to do with the nature of the Wrights' relationship and a motive for the crime. But since the women knew they would have no voice in the matter, they kept that revelation to themselves. The men continued to look for hard evidence. This is an example of dramatic irony which is when the audience is aware of the fact that the women are finding real clues while the men strut around with undeserved authority, finding essentially nothing significant.
This idea that men should attend to public affairs and women should not is now considered an outdated and misogynistic philosophy, but it was a part of the ideology and culture of male/female relationships in America well into the 20th century. "Trifles" was written in 1916, four years before the 19th amendment was passed which acknowledged women's right to vote.
The women's suffrage movement, the struggle to give women the right to vote, is an important historical anecdote because this play is about the role of a woman's voice. In "Trifles," the women find all the clues that are of any significance. Yet, the men dismiss everything the women say because they (the men) believe that women's opinions should be relegated to knitting, cooking, etc. The men don't see (because of their bias with regard to these traditional gender roles) how a woman can give analytical advice; certainly not any logical observations of something as important as a crime scene. Mrs. Hale and Mrs. Peters do not offer their evidence because they realize it would be laughed at and because they feel sympathy for Mrs. Wright (and are therefore, protecting her).
If women had a voice that men respected, within the context of the play, the crime would have been solved quickly. Going back prior to the crime itself, if women had more opportunity to work in the public world, perhaps Mrs. Wright would have left her husband long before any such crime would have occurred.