The term derives from carnal, meaning "of the flesh," and the Biblical usage of the verb know/knew, a euphemism for sexual conduct.
- "And Adam knew Eve his wife; and she conceived, and bore Cain, and said, I have gotten a man with [the help of] Jehovah." — Genesis 4:1.
- 5 And they called unto Lot, and said unto him, Where are the men that came in to thee this night? bring them out unto us, that we may know them.
- 6 And Lot went out unto them to the door, and shut the door after him.
- 7 And he said, I pray you, my brethren, do not so wickedly.
- 8 Behold now, I have two daughters that have not known man; let me, I pray you, bring them out unto you, and do ye to them as is good in your eyes: only unto these men do nothing, forasmuch as they are come under the shadow of my roof. — Genesis 19:5-8.
In criminal law, the term has had different meanings at different times and in different jurisdictions. While commonly a mere euphemism for sexual intercourse (not necessarily unlawful), different jurisdictions have defined carnal knowledge (as well as sexual intercourse) as a specific sex act such as contact between a penis and vagina, some laws elaborating this to include even "slight penile penetration of female sex organs." The definition sometimes includes a set of sex acts that include sodomy, while some statutes specifically exclude such acts. Some laws do not define the term, and leave it to the courts to give it meaning, which also allows them to take into account changing community standards.
Carnal knowledge has also sometimes meant sexual intercourse outside of marriage, and sometimes refers to sex with someone under the age of consent. The phrase is often found in this sense in modern legal usage, being equivalent to statutory rape in some jurisdictions, as the term rape implies lack of consent.
A related term is carnal abuse, which is defined by Dictionary.com as "any lascivious contact with the sexual organs of a child by an adult". Usually, but not always, this does not involve penetration.
England and Wales
Section 18 of the Offences against the Person Act 1828 reads as follows:
What shall be sufficient Proof of carnal Knowledge in the Four preceding Cases. XVIII. 'And Whereas upon Trials for the Crimes of Buggery and of Rape, and of carnally abusing Girls under the respective Ages hereinbefore mentioned, Offenders frequently escape by reason of the Difficulty of the Proof which has been required of the Completion of those several Crimes;' for Remedy thereof be it enacted, That it shall not be necessary, in any of those Cases, to prove the actual Emission of Seed to constitute carnal Knowledge, but that the carnal Knowledge shall be deemed complete upon Proof of Penetration only.
The crimes of carnally abusing girls referred to were those created by section 17 of the Act.
In cases decided under this section it was held that the slightest penetration was sufficient.
This section was replaced by section 63 of the Offences against the Person Act 1861. The term was not used in the Sexual Offences Act 1956, which replaced it, where it appeared, with the term sexual intercourse, in all the provisions consolidated by that Act.