In the story the detctives do not suspect Mrs. Maloney of killing her husband because her gender roles as a woman are being fragile, dumb, incapable of doing anything that needs physical force, does nothing but cook, clean, take care of the house, tend to her husband, and above all she is pregnant which helps her get away with murdering her husband. Mrs. Maloney is the typical house wife that always tends to her husbands every need. When she kills her husband and the detectives come to her house to investigate his murder they do not expect her to have done such a thing.
The detectives believed that her husband was hit behind the head with a heavy blunt object and her gender role being a woman let alone a pregnant woman help her get away with murder. Since she's a pregnant woman her gender role helps her seem fragile and weak Incapable of carrying a heavy object and exerting enough force to kill someone, so that's one of the reasons she gets away with murder. Another reason Mrs. Maloney gets away with killing her husband is that she basically worshipped him, she lived for him. Mrs.
Maloney did everything she possibly could make her husband a happy man, the way it should be in those times. In the story it shows how much Mrs. Maloney loved her husband, and how she enjoyed being a house wife. The police officers and detectives notice that Mrs. Maloney seemed to be grieving over her husband's death, and they didn't know about Mr. Maloney's intentions on leaving Mrs. Maloney, so it makes her look less suspicous. Last but not least Mrs. Maloney was a smart woman, and created an alibi. Men in those times thought women were dumb, and they were also supposed to be virtuous and innocent.
So when the detectives questioned her she had the perfect alibi. To men a woman could have never been able to do such a thing because they were too innocent, and since they were considered dumb they knew she would've been caught if they would have killed someone. In Conclusion, the gender roles of women played a large role in the story because it hepled Mrs. Maloney get away with murdering her husband. The detectives obviously had stereotypes about her being the typical house wife and she played along, so Mr. Maloney's murderer will remain a mystery.