धारा 91

Nothing which is not intended to cause death, or grievous hurt, and which is not known to the doer to be likely to cause death or grievous hurt, is an offence by reason of any harm which it may cause, or be known by the doer to be likely to cause, to any person above eighteen years of age, who has given consent, whether express or implied, to suffer that harm, or by reason of any harm which it may cause, or be known by the doer to be likely to cause to any person below eighteen years of age, or to any person of unsound mind, who has given consent, whether express or implied, to suffer that harm, if that person is competent to understand the nature and consequence of that harm.