There is more authorial intrusion in the short story "A Jury of Her Peer" than in the play Trifles. As such, Glaspell reveals many more of her characters' feelings in the short story. She leaves the emotional subtext for the actors to reveal on stage.
So says one critic:
For example, on page 275 the writer explains how Mrs. Hale first met Mrs. Peters, “the year before at the county fair”. Mrs. Hale’s opinion of Mrs. Peters is brought to the surface on page 276 when the writer reveals that she felt Mrs. Peters “didn’t seem like a sheriff’s wife”. Whereas in the play Trifles, the reader is left with no insight of this nature since the dialogue is so central (all you know is what you see and hear). Feelings are left out of the play, and revealed in the short story.
Another obvious difference is the title. The play's title Trifles is more subtle, whereas the short story's title "A Jury of Her Peers" basically reveals two major themes from the start: feminist community ("her Peers") and legalism ("Jury"). Trifles is wonderfully ironic: it is what the men think of women's work. As such, its title better reveals the little things (the clues and subtext), which drives this psychological play.
The women are marginalized more in the play. They are physically segregated from the men, and their presence on stage keeps them--as a community--front and center. No one woman is more important than the other. Even though it is titled Trifles and not "A Jury of Her Peers," the play's grouping of the women allows them to be more of a physical jury. This is more symbolic and meaningful.
Audience participation, I feel, is the biggest difference. Quite frankly, the short story gives too much away. It's too easy, too seamless. The play, even if it is read and not seen, is much more like a detective story. As a reader or viewer of the play, we have to use more deductive reasoning and fill in the pieces to the mystery.
Martha Hale is the central figure in the narrative, whereas in the play she is major but not dominant. In addition, much information about Martha is introduced into the story easily and naturally because she is the focus of narrative attention, whereas in the play this material is less justifiable because Martha is only one person among many. The major character, about whom the story revolves, is Minnie Wright, who is suspected of murdering her husband. But in the development of the story, the major acting and speaking character is Martha Hale. These two versions show the power of prose and the range of dialogue, both effective tools in the production of their own forms of genre.