From the Introduction (pages 61 Buffalo L. Rev. 997-1007; footnotes omitted):
 
Introduction
 
In the late 1850s, Daniel Edgar Sickles, a congressman from New York, received an anonymous letter with shocking news.  Sickles was a married man. His attractive wife, Teresa Bagioli, was much younger than Sickles-he was 37; she was about half his age. Your wife, the letter said, is carrying on an affair with a man named Philip Barton Key.  The letter disturbed Sickles greatly. Sickles confronted his wife and asked her whether the letter told the truth; tearfully, she admitted that it did.  She confessed that she used to meet with Key in a house on Fifteenth Street, where she “did what is usual for a wicked woman to do,” on a bed on the second floor. Sickles was a man of action. He took his guns and looked for Key on the streets of the capital.  When he found him, he shouted, “Key, you scoundrel . . . you have dishonored my bed-you must die!”  And Key did die; one bullet pierced his thigh, another his liver.  Sickles was arrested and charged with first-degree murder.  At the end of the trial, the jury, in almost indecent haste, brought in a verdict of not guilty. 
 
Fifty years later, Margaret Finn shot and killed J.E. Mahaffey on a crowded Los Angeles Street.  Finn and Mahaffey were engaged to be married.  Moreover, Finn was pregnant with Mahaffey's child.  But Mahaffey was having second thoughts. He was running out of money, he told her, and wanted to postpone the wedding indefinitely.  Devastated by the scoundrel's betrayal, Finn found a revolver, tracked Mahaffey down, and shot him dead.  She claimed that she could not remember firing the gun. Her mind had gone totally blank: what happened was “a mystery.”  Still, she refused to apologize: “I had placed my honor and my life in his trust and he betrayed that trust . . . .”  Mahaffey “deserved death for the way he treated me.” The judge agreed. He dismissed the case against her without trial. 
 
And on January 13, 1912, John Beal Sneed, a member of a wealthy Texas family, shot and killed Captain Al Boyce Sr., a millionaire banker, in the lobby of the Fort Worth Hotel.  Sneed's young wife, Lena, was in love with Boyce's son, Al Jr., whom she had met while they were students together at Southwestern University.  Lena confessed to her husband that she was in love with Boyce and sought permission to run away with him to South America.  Instead, Sneed committed her to a nearby sanitarium.  But Al Jr. arranged for her to escape, and the couple eloped to Canada, where they hoped to start a new life together.  It was not meant to be. Sneed learned of the escape, retrieved Lena, and returned to Texas-humiliated, jealous, bent on retribution.  Convinced that Boyce Sr. had helped his son, Sneed shot the old man, claiming afterwards that “it had to be done.”  He was tried for murder, but the jury could not agree on a verdict. A mistrial was declared.  Before Sneed could be retried, he tracked down Al Jr. in front of a Methodist church in Amarillo, Texas. Disguised as a tramp “with a heavy growth of beard and wearing overalls,” Sneed shot the younger Boyce.  Wounded and bleeding, the victim pleaded with Sneed to spare his life, but Sneed shot him again.  “I guess you are dead,” he said.  A jury acquitted him of both killings.
 
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These three cases are illustrations of the so-called “unwritten law.” The phrase refers to a phenomenon that can be traced back to the middle of the nineteenth century. As applied to trials like the trial of Daniel Sickles, it had a clear social meani