Dead in the Water by Stuart Woods

Dead in the Water: A Novel (Stone Barrington) - Stone Barrington is in St. Marks, a Carribean island, waiting for Arrington to join him.  On the yacht he has rented he sees a much larger yacht enter the marina crewed by a lone woman.  Later, he learns that her husband had died at sea and there would be a inquest. Nothing better to do, he attends the inquest.  As the inquest proceeds, he sees that Sir Winston Sutherland, the minister of justice, has decided that the woman, Allison Manning, is guilty.  Sutherland proceeds to use his position to railroad Allison.  Stone does everything he can to prove that Allison is innocent but he is constrained by the the old fashion laws of St. Marks.