The basic plot of this story, which becomes the play, Trifles, is a woman by the name of Minnie Wright has killed her husband, John Wright. They live in a secluded farmhouse, and he is not kind to her. He even kills her canary which the reader assumes was the one bright spot in her hard and isolated life.
John is already dead and moved from the house. In fact, we never even meet Minnie. We get to know her from the state of her house, the comments the women who are in her house make, and the items she asks them to bring to her in the jail.
The women go to the house with their husbands--they are the neighbors and the sheriff's wives. The men leave the women to "women's things"--the little things that are important to them, not necessarily to the men. The men are looking for clues.
It is ironic, then, that the women are the ones who find the evidence which will condemn Minnie to hang for murdering her husband. They make a decision to protect her and hide the evidence from the men. This is why the story is called "A Jury of Her Peers"--the women are Minnie's equals and know what she goes through on any given day.
The play which is later developed from the story, Trifles, is titled because the "little things, or trifles" of the women's lives are what serve as the evidence which, if found, would cause Minnie to go to jail or hang for murder.
We do not know how the trial came out, but we assume she went free.