Original Sin Murders

What is injury and can be dealt with through ordinary means? And what is insult and must be opposed, with violence, if necessary. A college basketball player whose family was cheated out of its wealth takes no action against the family who swindled them. Yet, when a dinner served at their table is poisoned, she is charged with the crime and the detectives must find evidence to acquit her of the charges. The solution lies in Edgar Allan Poe's opening line of A Cask of Amontillado 'The thousand injuries of Fortunato I bore as best I could; but when he ventured upon insult, I vowed revenge.' How can they solve a case when they believe that their client is guilty?