Duhaime's Law Dictionary

M Definition:

Ancient common law: the symbol branded on the thumb of persons convicted of manslaughter.

Related Terms: Manslaughter

Giles Jacob's Law Dictionary, published in 1811, defined the letter M in a legal context as follows:

"M is the letter with which persons convicted of manslaughter are marked on the brawn of the left thumb."

In the well-known trial of British Kilroy (his attorney was the future president of the United States, John Adams), Kilroy was charged with murder but found guilty of the lessor offence of manslaughter. According to the Boston Massacre Historical Society:

"Kilroy ... faced the death penalty at the sentencing on December 14, 1770. To escape execution (he) prayed the benefit of clergy, a Medieval remnant of the time when clergymen were excepted from the secular courts. To receive the benefit (he) had only to prove they could read Psalm 51, verse 1..... Although illiterate himself, Kilroy was able to obtain the benefit because the reading requirement was abolished in 1705. Suffolk County Sheriff Stephen Greenleaf branded Kilroy ... on the right thumb with an "M".... The brand was to prevent (him) from ever being able to invoke the benefit of clergy again."


  • Boston Massacre Historical Society
  • Jacobs, Giles, The Law Dictionary Explaining the Rise, Progress and Present State of the English Law; Defining and Interpreting the Terms or Words of Art and Comprising Copious Information on thre Subjects of Law, Trade and Government (Philadelphia: Riley & Byrne, 1811)

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