The play Trifles (1916) was appropriately titled "A Jury of Her Peers" when made into a short story adaptation of the play in 1917. The reason why the title fits the story so well is because of the situational irony of the story.
Minnie Wright, who snaps and murders her husband after years of physical and psychological abuse, ironically does end up getting an impromptu and speedy "trial" led by a jury of her peers: the only two women present in her household while it is being investigated as a crime scene, and who also understand Minnie's situation, Mrs. Hale and Mrs Peters.
Mrs. Peters is the wife of the sheriff investigating the crime scene. Next to her is Mrs. Hale, who is the wife of the farmer assisting the Sheriff and District Attorney as a witness. When both women realize that the clues that could put Minnie in jail are all over the house, they choose to hide the evidence thus helping Minnie to have a shot at freedom.
This is because the two women have also experienced a certain lack of freedom of their own; one that comes with the burden of being a female in a male dominated society that cares very little for their needs.
Lack of freedom:
An example of the lack of freedom that Mrs. Peters experiences is the immediate assumption that Henderson makes (and people like him) that she is basically married to the law, that she is a mirror of her husband, and that she is there to obey and serve as well. The reader learns that Mrs. Peters has always lived under the shadow of her husband and his job; she would never be able to move away from a set path due to the expectations put upon her. Yet, she does have a side that she aims to liberate; she wishes to have a voice--but it has always been muffled.
[In a whisper] When I was a girl--my kitten--there was a boy took a hatchet, and before my eyes--and before I could get there--[Covers her face an instant.] If they hadn't held me back I would have--[Catches herself, looks upstairs where steps are heard, falters weakly]--hurt him.
She is fully aware that society aims to hide, trap and control women rather than encourage their social liberation. This is how she can make a connection to the case of Minnie Wright; she was trapped to the point of asphyxiation, and she snapped as a result.
Mrs. Hale has not experienced the lack of freedom to the degree of Mrs. Peters, but she is quite aware of the woes of Mrs. Wright after she got married.
Minnie, who was once a cheerful, talented and free woman quickly became a shadow of her former self. She was literally imprisoned in her own home with her husband serving as both her guard and terrorist. Mrs. Hale describes Minnie's husband as a "hard" and cold man. She compares Minnie, who sang beautifully, to a bird trapped inside of a cage. Upon realizing that there was actually a bird in the house, and that Minnie's husband wrung its neck, it is clear that the comparison was quite fitting.
I could've come. I stayed away because it weren't cheerful--and that's why I ought to have come. I--I've never liked this place. Maybe because it's down in a hollow and you don't see the road. I dunno what it is, but it's a lonesome place and always was, I wish I had come over to see Minnie Foster sometimes. I can see now--
Therefore, by hiding the evidence that puts Minnie at the epicenter of the case, Mrs. Peters and Mrs. Hale are moving away on a tangent from the expected behaviors of "good" wives in order to help one of their own get the freedom that she deserves. They feel the need to help Minnie try and get a chance for freedom away from an abusive husband, and from a society that would attack her whether she was the victim or not. Their actions are quite significant because they, too, are trapped in the same society. They are also suffering from a lack of freedom of a sort. Hence, they are making a difference for someone.