To go all serious business with you: Assuming this was published in the 50s, 27 women had been given death penalty by electrocution between 1909 and 1957, five of them in New York alone, so the idea that she if she'd been convicted of murder, she could fry isn't totally off the rocks. Also, spousal abuse as a defense still isn't recognized in most states except as part of a plea of self-defense. At the time that this story would have taken place, the mother couldn't have pled self-defense anyway unless there was a witness who could claim that the husband was attacking her physically at the time she shot him. In fact, Steve's presence would have even killed that defense in the water, since the assumption during the time period would have been that he should have protected her instead of her using the gun.