What is clear is that throughout this play we as an audience and Mrs. Peters are given valuable information about the murder suspect, Minnie Wright, including her background and how she has been oppressed by John Wright, her husband. This is what Glaspell uses to crucially gain sympathy in us for Minnie Wright which means we automatically side with Mrs. Peters and Mrs. Hale at the end of the play when they join together in solidarity with Mrs. Wright to remove any evidence of motive for her killing her husband and enable her to go free.
Note how Mrs. Hale reveals lots of details about Minnie Wright before she got married and then how she changed:
She used to sing real pretty herself.
She - come to think of it, she was kind of like a bird herself - real sweet and pretty, but kind of timid and - fluttery. How - she - did - change.
Notice here how Mrs. Hale is explicity comparing Mrs. Wright to a bird, and how her description is meant to gain sympathy for her, using words that emphasise her fragility and weakness: "timid" and "fluttery". The dashes in her last sentence clearly emphasise the change under Mr. Wright, who was described by Mrs. Hale as "Like a raw wind that gets to the bone".
The discovery of the dead bird bring this full circle - we see that metaphorically Minnie is the bird who has been killed cruelly - if not literally, in every other sense, by the harshness of her husband, and thus we side with the women in their act of hiding the evidence and removing any motive.
I did 2 research papers on this work, and i got a full mark on the two of them, so here's a short qoute:
"Maybe it's unusual to see a victim commits murder, shows no emotions, but this was the interesting thing about Trifles. At the beginning of the play, Glaspell wanted her audience to see Mrs. Wright as a bad, insensitive, emotionless woman, then; the audience is forced to see the world through the eyes of Mrs. Hale and Mrs. Peters to understand the reasons that made Mrs. Wright kills her husband. This is what makes this play unique and ahead of it's time."
hope u find it usefull and good luck ;)