Age of consent
In Canada, the age of consent is 16 years (s. 150.1 criminal code). A 16 year old can legally consent to sex with 62 year old. Prior to 2008, the age of consent was 14 years. There is an exception to this in cases where one person is in a position of trust towards the other. For this reason, a 16 year old likely cannot consent to sex with her 42 year old teacher.
Mistakenly believed girl was legal age to consent
Some individuals wind up charged with sexual assault after having sex with a 14 or 15 year old they believed to be 16 years of age. The criminal code limits this defence to circumstances where the accused took “all reasonable steps” to ensure the victim was of proper age. Just because a girl says she is 16 is not necessarily enough to meet this definition.
For example: Two 15 year olds attend a college party and claim to be at least 16 years of age. One of them has sex with an 18 year old at the party. The next morning, the girl who had sex returns home and her mother questions her about what she did last night. The girl admits to having sex and the mother takes her to the police station to give a statement. After this, the guy is confronted by police in his dorm room and charged with sexual assault.
In this case, the court is going to look for evidence that he took “all reasonable steps” to ensure the girl was old enough to consent to having sex. If she didn’t mention her age, and he didn’t ask or attempt to find out how old she was, he likely would be found guilty. The court is going to assess factors like what the accused knew about her background, how old the girl looks, whether she was engaging in activities indicative of age like driving a car or entering nightclubs, etc.
Since the criminal code is so open and generally worded there is no specific definition of what taking “all reasonable steps” actually means. It is certainly not safe, however, to assume that a young looking girl is telling the truth about her age if you have no other information about her background.