The information the reader receives about Minnie Wright comes from the conversation between the men and Mrs. Hale and Mrs. Peters, but we can draw some valid inferences in her defense in court as to why she was driven to kill her husband. It would still be difficult to prove her innocence, given the social norms of that male-dominated society that believed that the daily chores the women carry out, even the women themselves, were "trifles."
Minnie could have used several aspects of her life with Wright to defend herself—first, a psychotic break or temporary insanity. Glaspell introduces the idea of mental instability when the sheriff makes a reference to "insanity," which could allude to Minnie's state of mind. He reports that someone had to go to Morris Center to deal with a man "who went crazy." When Hale arrived at the Wrights' home, Minnie was acting crazy herself...rocking back and forth in her chair, "pleating" her skirt. He notes that she looked "queer" and "kind of done up" (done in or wiped out).
Minnie's state of mind is further evidenced by Hale's report of Minnie's odd behavior. He had told Minnie that he wanted to see her husband and she laughed, but it sounded peculiar to Hale. When he asked to see Wright, Minnie told Hale that Wright was dead:
"Dead?" says I. She just nodded her head, not getting a bit excited, but rockin' back and forth.
Speaking to Minnie's state of mind, Mrs. Hale notes of their home:
It never seemed a very cheerful place.
And when the attorney comments on Minnie's "homemaking instinct," Mrs. Hale responds:
Well, I don't know as Wright had, either...I don't think a place'd be any cheerfuller for John Wright's being in it.
We learn more about the marriage; Mrs. Hale says:
Wright was close [stingy]. I think maybe that's why she kept so much to herself...you don't enjoy things when you feel shabby.
Minnie could argue that she lived a harsh life. Hale tells Mrs. Wright that he came to see if her husband would split the cost of a phone line with him—and Minnie laughs outright. Mrs. Hale has already reported that Wright was stingy. We can infer that his wife believes it preposterous that he would ever agree to share the cost of anything with anyone.
Hale reports that Minnie looked scared. This could be a sign of her guilt, but one wonders if she was fearful of her husband: his rage is obvious when the women find the birdcage; they note that someone has been "rough" with it. Wright's propensity toward violence is obvious when the women find the dead bird. It was intentionally killed.
MRS. PETERS. Somebody--wrung--its neck.
The threat Wright presented is frightfully apparent as Mrs. Hale speaks of "killing."
No, Wright wouldn't like the bird--a thing that sang. She used to sing. He killed that, too.
Here is a strong inference that Wright was a violent man. Mrs. Hale believes he was a threat. Minnie could have argued that she feared for her life.
Mrs. Peters also notes how lonely the house is; Minnie never had children.
Mrs. Hale reflects on life with Mr. Wright:
...he didn't drink, and kept his word as well as most...and paid his debts. But he was a hard man, Mrs. Peters. Just to pass the time of day with him. (Shivers.) Like a raw wind that gets to the bone.
These details, reported by other characters, would provide a number of pertinent facts aiding in Minnie's self-defense for killing her husband: emotional (and physical?) abuse, loneliness, and mental instability.
In considering what Minnie Wright will give as her defense, the student may wish to establish that Mrs. Wright has had consultations with a psychiatrist prior to her writing because as a rather uneducated woman it seems apparent from the narrative of the drama that she may not realize exactly how to present her defense. For, Mrs. Wright suffers from what is termed Battered Spouse Syndrome; that is, she has been psychologically abused.
With this psychological battering in mind, then, the student can have Mrs. Wright address the cruel treatment of her husband, who has deprived her of the aesthetic [perhaps Minnie would use the word beauty and gentleness for this word], leaving her existence barren of any pleasure. In essence, Mrs. Wright has become a mere slave in her own house; for, she exists only to cook and clean.
One way to begin Minnie's defense is by her writing, "I have been asked why I was rocking back and forth, pleating my apron with a distant, scared look upon my face when I told Mr. Hale to come in? I do not remember. I only remember that my pretty, little canary died--strangled! The only beautiful thing in my life!....I don't know what really happened." (She is in denial as she has told Mr. Hale she did not know who killed Mr. Wright. For,it is apparent from the initial dialogue of the County Attorney and Mr. Hale that Mrs. Wright was unaware of her action of killing Mr. Wright. For, she is not focused on reality, and she tells Mr. Hale that "Somebody slipped a rope round his neck and strangled him," but she did not wake up.)
Then, the student may wish to have Minnie write that when she spoke with the doctor (psychiatrist), she was asked to explain what her life with John Wright was like. She thinks that maybe she should put these things down since the doctor seems to believe they are important. Minnie then writes about her life as a lonely farm wife, including the details that are given in the play such as her sewing and canning, which seem to have given her joy. But, the isolation [she may call this loneliness] was too much to bear, especially when she no longer could sing--she could write "the music just wouldn't come from me, anymore"--and then lost the music of her bird. Even when she tried to sew, she could not always make uniform stitches.
Clearly, then, the writer for Minnie must establish that she has lost her awareness of reality because it has been so unbearable for her as a mentally abused woman. To do so, the writer will want to include the above-mentioned issues and details in such a way that Mrs. Wright yet appears insensate and aberrant in her thinking.
[Below is a link to an answer that is relevant to the writing of this letter.]