The Pink Pony: Murder on Mackinac Island - Charles Cutter

The world-class Port Huron-Mackinac sailboat race has just finished at Mackinac Island. As soon as the boats dock, the sailors head for the legendary Pink Pony. But the night takes a grisly turn, and Jimmy Lyons is found dead the next morning in the bar, strangled by a string of Christmas tree lights.
Murdo Halverson, a wealthy manufacturer from Detroit and Jimmy's former partner, is arrested for the murder. It turns out that the free spending Jimmy was broke. Each of his crew, including Murdo, had a reason to kill him. As did his wife, Jane.
Burr Lafayette, recently divorced and the deposed head of the litigation department of a major Detroit law firm, is recruited to defend Murdo by his wife, Anne, and his mother, Martha, the widowed matriarch of the family.
A man at loose ends, Burr is a brilliant litigator who prefers boats and dogs over courtrooms and clients. But he's not a criminal lawyer, and this looks like a losing case. Did Murdo kill Jimmy or was it someone else?