A criminal offence under the Sexual Offences Act 2003, in which a person (A) intentionally penetrates the vagina or anus of another person (B) with part of his body or anything else, where the penetration is sexual, where B does not consent to the penetration, and where A does not have a reasonable belief that B consents. Whether A's belief in B's consent is reasonable is to be determined having regard to all the circumstances, including any steps A has taken to ascertain whether B consents. The * mens rea element for assault by penetration in the 2003 Act sets a standard of negligence whereby the defendant's honest but unreasonable belief in his victim's consent will not negate liability. Formerly, the defendant's honest belief in the victim's consent would negate liability, irrespective of whether that belief was reasonable (DPP v Morgan  AC 182 (HL). The maximum penalty for assault by penetration is life imprisonment. Unlike rape, which can only be committed as a principal by a man, assault by penetration can be committed as a principal by both men and women. See also sexual assault.