Female attorneys andsheriffs, and male homemakers are fairly common these days so how would the characters and setting change for a 21st century audience
The only real way this story could be retold with any accuracy or integrity in a modern time would be if it were set in some kind of small, backward environment. I agree with above posts that someplace rural might work, or even some kind of patriarchal cult or society--any place where men can still dominate and abuse women with impunity. Thankfully, these places--in America, anyway--are more difficult to find than they used to be.
I agree with akannan on this one. There are definitely some contexts - perhaps in rural America - where the issues of gender stereotyping, chauvinism and patriarchy are still prevalent, but in a lesser form. The world has, thankfully, moved on a lot since those days of widespread female oppression, and so there is a lot more support out there for women. So I guess it would work, but not as effectively as the original Trifles. Interesting question to think about though!
I think that you could still stage the play in an area where the "traditional" roles of women are still evident. It would be a diluted form, and certainly not to the level of stereotyping as displayed by the men in the play. Yet, there are still some areas where the notion of how women are perceived and how they are to interact that has some reflections of the setting in the play. Part of the reason for it being diluted would lie in the accounting for technological changes that would have to be present. I think this would be something that would have to be added into a new staging of the play.
Trifles, the play by Susan Glaspell, was also written by the author as a short story titled "A Jury of Her Peers". You might find that helpful.
However, keeping the title of both the play and story in mind, we might find that Trifles is impossible to play taking the sexist feelings of the early 1900's out because that really is what constitutes the play. It really is a piece from and about that time period.
One way that could be done (but this would greatly alter the play) would be to have the characters unrelated and have their reasoning be ruled as trifles because of their race, sexual orientation, or religion. It would take a major re-write, but it could be done.
I also feel that it would be impossible to have the play changed for a 21 century audience. I wonder if the roles were reversed meaning the women be the ones investigating the crime scene and the men being the "submissive" roles if that would work. As for the setting I'm not sure how it would change. Any ideas are appreciated.