How do Mrs. Peters and Mrs. Hale view "the law" and "justice" at the begining and end of Trifles by Susan Glaspell?
In Susan Glaspell's play, Trifles, the women go to the Wrights' home on "official business"—to collect things Minnie Wright might need while in jail, suspected of murdering her husband. In doing so, the women find a distinction between the "law"—which would find Mrs. Wright guilty—and "justice," which allows for extenuating circumstances.
Mrs. Hale (Minnie's neighbor) and Mrs. Peters (the sheriff's wife) arrive to collect a change of clothing and maybe some sewing. More insightful of the world in which Mrs. Wright lived, the women grow to understand her circumstances much more clearly than the men, who find that keeping house and putting up preserves are "trifles" that occupy a woman's day.
When they arrive, the women see "the law" in black and white. However, while listening to the men and their dismissive attitudes, Mrs. Hale and Mrs. Peters become more sympathetic to Mrs. Wright. It starts with Mrs. Wright's broken jars of preserves.
MRS. PETERS (to the other woman). Oh, her fruit; it did freeze. (To the Lawyer). She worried about that when it turned so cold. She said the fire'd go out and her jars would break.
SHERIFF. Well, can you beat the woman! Held for murder and worryin' about her preserves.
COUNTY ATTORNEY. I guess before we're through she may have something more serious than preserves to worry about.
HALE. Well, women are used to worrying over trifles.
(The two women move a little closer together.)
The movement of the women shows their quiet displeasure upon hearing a task that takes time and hard work to complete referred to as "trifles," something unimportant.
When the County Attorney complains about dirty kitchen towels, Mrs. Hale becomes defensive.
MRS. HALE (stiffly). There's a great deal of work to be done on a farm.
As the story continues, Mrs. Hale provides insight into Mrs. Wright's life. She agrees that the house was not cheerful-looking, but it would be quite a task to make it so with John Wright living there. She also comments that John Wright was "close" meaning "cheap." With no children, Mrs. Wright was probably exceedingly lonely, they believe.
The women are told to look for clues.
But Mrs. Hale and Mrs. Peters will be unable to do so.
COUNTY ATTORNEY. ...I would like to see what you take, Mrs. Peters, and keep an eye out for anything that might be of use to us.
The men laugh repeatedly as they move about, criticizing Mrs. Wright's housework. The women resent this. They know how hard it is to keep a home. Soon they find a possible clue regarding Wright's death—a birdcage that seems to have been violently broken apart.
MRS. PETERS. (examining the cage). Why, look at this door. It's broke. One hinge is pulled apart.
MRS. HALE. (looking, too.) Looks as if someone must have been rough with it.
In the sewing basket...
MRS. HALE. ...(Opens box...) Why...There's something wrapped up in this piece of silk...
MRS. PETERS. It's the bird...Somebody--wrung--its neck.
It doesn't take long for the women to conclude that the bird was killed by Mr. Wright. And Mrs. Peter recalls something from her past...
When I was a girl--my kitten--there was a boy took a hatchet, and before my eyes...If they hadn't held me back, I would have...hurt him.
Though dutiful to a point, the women cannot rationalize John Wright's actions. They feel Minnie was provoked and they remain silent, offering no help to the men. The women see a need for "justice" for Mrs. Wright, while the men can only see "the law."
Your question contained more than one part, so I had to edited it down according to enotes rules.
Mrs. Hale and Mrs. Peters act as the wives of a policeman and a prosecutor are expected to act. They are truly in support of their husbands, viewing any action pertaining to the letter of the law in line with complete justice. To them, and society, breaking a law means punishment, no matter the circumstances.
By the end of the play, the condescending and placating attitude of the men toward the women has made them reconsider their position. By this time, they have discovered Minnie's motive but have not revealed it to their husbands. The joking about women's "tifles," such as knitting has upset them and caused them to think about the treatment Minnie must have received from her husband. Thus, siding with her, they keep the motive to themselves, considering the situation of the murder rather than the concept of the murder itself.