Henderson attended the
University of Toronto and was called to the bar in 1893. He mainly practiced his profession alone, except for a few years when he was a member of the law firm Fripp Henderson & McGee. Henderson was the
Crown attorney of
Perth,
Pembroke, and
L'Orignal before 1906. He became a very well-known criminal defense lawyer in Ontario. J. P. Madden said, "It would be difficult to find a case which could be tried under the criminal code in which Dr. Henderson had not appeared." M. J. O'Connor said of Henderson, "His long and brilliant career reflected high honor on the bar of Canada." Upon his appointment of
King's Counsel, in 1929, he was described as "very prominent as a criminal lawyer and had many notable cases. In addition to successfully defending many accused, he has also acted as Crown prosecutor."
Duncan MacTavish said of him, "His career at the bar extended over a period of many years and was marked by a large measure of success, particularly in jury and criminal cases. By his death, the Bar of Ottawa has lost one of its most widely known and popular members." Henderson was noted as being somewhat eccentric. He did not have a telephone, calling it "a terrible waste of time." Upon his appointment to King's counsel, the newspaper described him as "radical and iconoclast."
Notable Cases Henderson was the Crown Prosecutor of Clement Goyette, who was hanged for murder. After this case, Henderson only defended clients. He defended Annie Balcomb, who was charged with murder for performing an illegal abortion. She was acquitted. Henderson defended Patrick Mahoney, an Ottawa police officer charged with murder. Henderson was senior counsel for the defense of
Louis Auger after he was accused of raping a young woman in the
House of Commons. == Political career ==