Duhaime's Law Dictionary

Incest Definition:

The crime of sexual contact with a blood relative usually including a parent, child, sibling, grandparent or grandchild.

One of the oldest crimes known to man; conduct prohibited and usually punished, since the very first law codes thousands of years ago.

Bouvier wrote in his 1897 Bouvier's Law Dictionary that the first statutory definitions focused on prohibited degree in regards to marriage. He defined incest as:

"The carnal copulation of a man and a woman related to each other in any degrees within which marriage is prohibited by law....

"It ... seems not at common law to be an indictable offence."

Incest became a crime in England in 1908, the Punishment of Incest Act. The crime was defined as:

"... any male person who has carnal knowledge of a female person, who is to his knowledge his grand-daughter, daughter, sister or mother."

In the United States, incest is punished with varying degrees, a felony here, a misdemeanour there.

In Canada, the Criminal Code, at §155(1) defines incest as:

"... knowing that another person is by blood relationship his or her parent, child, brother, sister, grandparent or grandchild, as the case may be, has sexual intercourse with that person.... 'Brother' and 'sister', respectively, include half-brother and half-sister."

The word "knowingly" has been problematic and interpreted to prevent a conviction if the accused did not know the other person was a blood relative.

In Rex v Carmichael, the British Court heard John Carmichael's appeal of his conviction on two counts of incest with his daughter Sonia, alleged to have occurred between 1933 and 1937 and set out the principle that an accused may lead evidence to refute knowledge that the victim was his daughter.


  • Rex v Carmichael, [1940] 1 KB 630
  • R v Beddoes, 103 CCC 131 (1952, SKCA)

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