One of four people - two men (Ben and Carl) and two women (Dorothy and Evelyn) - was murdered.
The following facts relate to the people mentioned:
(a) Ben's sister argued exactly once with Dorothy's legal husband after the murder.
(b) Carl's sister argued twice with the victim's legal spouse after the murder.
Who was the victim?
(In reply to Solution with assumptions
1.You've posted assumptions, but did not provide a solution.
2. Another implicit and vital assumption is that there were two married couples, - otherwise the puzzle is not solvable.