Reasonable belief that the victim is over the age of consent In some jurisdictions it is a defense if the accused can show that he or she reasonably believed the victim was over the age of consent. For example, the age of consent in the US state of Delaware is 18, but it is allowed for teenagers aged 16 and 17 to engage in sexual intercourse as long as the older partner is younger than The enforcement practices of age-of-consent laws vary depending on the social sensibilities of the particular culture see above. Ages can also vary based on the type of calendar used, such as the Lunar calendar ,  how birth dates in leap years are handled, or even the method by which birth date is calculated. In both the United Kingdom and Western Australia, for example, the age of consent was originally 21 for same-sex sexual activity between males with no laws regarding lesbian sexual activities , while it was 16 for heterosexual sexual activity; this is no longer the case. For court cases on this, see here stepfather-stepdaughter and here brother-sister. However, where such a defense is provided, it normally applies only when the victim is close to the age of consent or the accused can show due diligence in determining the age of the victim e. Examples of such positions of trust include relationships between teachers and students. In these jurisdictions, it is illegal to have sexual intercourse outside of marriage, so the de facto age of consent is the marriageable age. Most jurisdictions have set a fixed age of consent. Close-in-age exemptions Some jurisdictions have laws explicitly allowing sexual acts with minors under the age of consent if their partner is close in age to them. Because legalizing incest would, by making a future sexual relationship more speakable and legitimate, potentially affect the family relationship even while the child is underage the view to which I tentatively incline? Jurisdictions use a variety of terms for the offense, including child sexual abuse , statutory rape , illegal carnal knowledge , corruption of a minor,  besides others. The Council of Europe Convention on Action against Trafficking in Human Beings which came into force in also deals with commercial sexual exploitation of children. I thought this would be a good opportunity for me to ask again a few questions I asked some years ago about adult-adult incest speaking specifically of parent-child, grandparent-grandchild, or brother-sister, and setting aside cousins and the like: Should the penalty be relatively light, on the theory that only consenting adults were involved much as the penalty for prostitution is relatively light? By Eugene Volokh January 23, Email the author Follow volokhc Father-adult daughter incest is in the news again; apparently incest among adults is not a crime in New Jersey though incestuous marriages are void , and a father-daughter couple is planning on moving to New Jersey for that very reason.