Mrs Hale first notes that Minnie was part way through putting her sugar away when she left the task unfinished. Mrs Hale finds this suspicious-
What had interrupted Minnie Foster? Why had that work been left half done?
The kitchen is revealed to be shabby and dirty, and the oven does not work properly. Mrs Hale understands that the drudgery of Minnie’s life must have been depressing.
I think maybe that's why she kept so much to herself. I s'pose she felt she couldn't do her part; and then, you don't enjoy things when you feel shabby.
Mrs Peters also begins to understand the impact of such an impoverished life-
She was startled by hearing Mrs. Peters say: "A person gets discouraged--and loses heart."
The two pieces of physical evidence that the women discover are the quilt and the dead canary. When they look closely at the quilt, they see her stitching indicates that Minnie’s mind was disturbed-
“The sewing," said Mrs. Peters, in a troubled way, "All the rest of them have been so nice and even--but--this one. Why, it looks as if she didn't know what she was about!"
The dead canary; strangled and hidden in Minnie’s sewing box, reveals Minnie’s motives for killing her husband. She evidently strangled her husband as he strangled her canary-
the eyes of the two women met--this time clung together in a look of dawning comprehension, of growing horror.