In any work of literature, the rising action comprises an event, or a series of minor events, that come together to move the action, the plot, forward.
In the story "A Jury of Her Peers", the event that sets off the story's dynamics occurs when the women, Ms. Hale and Mrs. Peters, start to find the so-called "trifles" that are actually evidence of the state of mind of Minnie Wright at the time of the commission of the murder of her husband.
Oh, well,' said Mrs. Hale's husband, with good-natured superiority, 'women are used to worrying over trifles.
The "trifles" which, according to the definition of the word, are assumed to be non-important things, are actually considerably important. For example, the frozen compote, shattered into pieces, is indicative of a woman who once could devote herself to canning and doing other household chores. The lack of care in keeping these projects together clearly show that something was going on in the household that rendered her unable to keep up.
"Her eyes made a slow, almost unwilling turn to the bucket of sugar and the half empty bag beside it. Things begun--and not finished."
The stitching is another sign of Minnie slowly losing her mind. It looks as frazzled as Minnie felt at the time. Finally, the dead canary is the final giveaway that Minnie's husband was terrorizing her to the point of making her snap.
Had the women not found these things, or made sense out of them, the proper conclusions would have never been drawn out of the behaviors that led Minnie to do what she did.