The Union Army: A History of Military Affairs in the Loyal Staes 1861-65:
Records of the Regiments in the Union Army; Cyclopedia of Battles; Memoirs
of Commander and Soldiers, Vol. III (New Jersey, Indiana, Illinois and
Michigan, published in 1908. Available online at
https://books.google.com/books?id=XVNLAAAAYAAJ
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Horace Heffren, who was tried on conspiracy charge in 1864, "was released
from arrest and discharged, and thereupon became an important witness for
the prosecution. The court found (William A.) Bowles, (Lambdin P.)
Milligan, (Stephen) Horsey and (Andrew) Humphreys guilty (of the charge of
conspiracy to overthrow the government) and sentenced the first three to
death. Humphreys was condemned to imprisonment for life." After the day
was fixed for their execution and preparations were commenced, President
Johnson commuted their sentence to imprisonment for life at hard labor in
the Ohio penitentiary. Later yet the president directed the discharge of
the prisoners.