The actual crime occurred in the bedroom as Mrs. Peters, the protagonist, claims that someone came to the bedroom and put a rope around her husband's neck and strangled him in his sleep. Not much is said about the bedroom, however. Much, however is said about the kitchen. Why? Because of the context of the story and the atmosphere that the author is trying to create of a home in which a submissive wife suddenly snapped. Hence, the description of the kitchen, the state of the kitchen, the reaction of the detective upon seeing it, and the defense of Mrs. Hale, the neighbor, over the state of the it are all components of the atmosphere of gender injustice.
How does the kitchen look? Messy. The hand towels are dirty (which the detective, a chauvinist himself , had to talk smack about). Then the jars of jams and jellies had apparently busted open and cracked, leaving another mess everywhere. Everything was untidy, food laying around, and unfinished stitch work. All this was a way to summarize that the poor woman was at the end of her wits. The detective, of course, put it like the case of an untidy, bad wife that wasn't worth anything. The defense of Mrs. Hale, consistently giving a reason behind all that was found, shows that she had an idea of what was going on.