Based on recollections from listeners who had been present at St. John's Church on March 23, 1775, William Wirt reconstructed Patrick Henry's "Liberty of Death" speech for his biography of Patrick Henry, first published in 1817 and reprinted about two dozen times in the nineteenth-century.
In addition to Henry's other biographers, scholars who have specifically discussed William Wirt's reconstruction of Patrick Henry's 'Liberty of Death' speech include:
Charles L. Cohen, "The 'Liberty or Death' Speech: A Note on Religion and Revolutionary Rhetoric," William and Mary Quarterly, 3d ser., 38 (1981): 702-717.
David A. McCants, "The Authenticity of William Wirt's Version of Patrick Henry's 'Liberty or Death' Speech," Virginia Magazine of History and Biography, 87 (1979): 387-402.
David A. McCants, Patrick Henry, The Orator (Great American Orators, no. 8) New York and Westport, Conn., Greenwood Press, 1990.
Lloyd J. Matthews, "Patrick Henry's 'Liberty of Death Speech' and Cassius's Speech in Shakespeare's Julius Caesar," Virginia Magazine of History and Biography, 86 (1978): 299-305.