Power and control could be motives too. In some families, the woman might feel powerless and use murder as a way to assert control. Or, if she was being abused in the family, she could have snapped and killed the abuser. Another possible motive could be protecting a secret. If she had a dark secret that someone was about to expose, she might murder to keep it hidden.
Jealousy could be a motive. Maybe she suspected her husband of infidelity and in a fit of rage, committed murder.
Jealousy could be a motive. An unlikely murderer might see someone else having what they want, like a relationship or a job opportunity, and out of envy, commit murder.
One possible motive could be revenge. Maybe the officer had a personal grudge against the victim. Another could be greed. If the victim had something valuable, the officer might have wanted it for himself.
One possible motive could be revenge. If the child had been severely mistreated by the mother, they might have lashed out in a very extreme way. Another could be mental instability, which made them unable to distinguish right from wrong.
Revenge could be a motive. Maybe she was wronged by someone in the past, and she disguises herself to target those related to the person who wronged her.
One possible motive could be protection. The mother may want to shield her family from a painful truth.
Power and control within the family could also be a motive. One sister wife may want to be the dominant figure and see another as an obstacle, so she resorts to murder to assert her authority.
One possible motive could be to reignite the passion in their relationship. Over time, the spark can fade, and a wife might seduce her husband to bring back that excitement. For example, if they have been married for years and fallen into a routine.
Perhaps the wife is just curious. She wants to understand what the mistress has that attracted her husband. So, she decides to get close to the mistress through seduction. In the process, she may hope to find out the mistress's secrets, her allure, and then use that knowledge to either win her husband back or to simply feel more in control of the situation. However, it's important to note that these are all rather complex and often unethical motives that exist more in fictional or extreme relationship scenarios.
One possible motive could be a sense of power or control. The wife may feel empowered by being able to attract a younger person. Another could be a form of escapism from her own marriage problems. She might be seeking excitement that she feels is lacking in her relationship with her husband.
One possible motive could be money. Maybe she was after an inheritance and decided to eliminate those who stood in her way.