In Trifles who are the protagonist and antagonist?
Such an interesting question! At first, it seems the protagonist is John Wright, the deceased, who has obviously (maybe) been murdered by his wife, Minnie Wright. This would make her the antagonist as she is the "murderer" and in clear violation of the law. Further, both of these characters are never on stage. The play begins with Mr. Wright's body having been removed and Mrs. Wright down at the Sheriff's station awaiting trial.
Now, on further investigation, the story flops. We see through the story of Mrs. Hale and Mrs. Peters that Minnie was a bright child, happy and carefree, who loved to dress up and sing. Her hard life, her isolation, and the fact (presumed from the evidence the ladies find) that John Wright broke the neck of her canary, drove her to kill him in the same way. This angle of argument creates pathos in favor of Minnie, who becomes the protagonist. John Wright, then, the cruel and abusive husband, is the antagonist who got what he deserved.
Ironically, the men who are in charge never see it this way, and they will never learn of the evidence their wives have discovered since the women are the true jury of Minnie's peers (this play was based on a short story by Glaspell called "A Jury of Her Peers"--all based on a newspaper story Glaspell read about a woman who allegedly killed her husband), and having related to Minnie on many levels, the women have found her not guilty. In this way, all the women of the play seem to be collectively the protagonist. The men, therefore, are collectively the antagonist as they do not see any importance in the women's "trifles" and the smallness of their lives. They are all, then, somewhat guilty of taking their wives for granted and not treating them with as much love and respect as they probably should.