B. (A Minor) v. Director of Public Prosecutions 1 All E.R. 833 (2000) B was a 15 year-old who attempted to coerce a 13 year-old into sex. He was arrested and charged with inciting a child to commit an act of gross indecency. At Trial, B argued that he had honestly believed the girl was over 14. The Trial Judge ruled that a mistake of fact could not constitute a defense. The Judge relied on Regina v. Prince (L.R. 2 Cr. Cas. Res. 154 (1875)). B pled guilty and then appealed. The British House of Lords reversed the Trial Judge and allowed the appeal. The House of Lords found that is necessary for the prosecution to prove the absence of a genuine belief on the part of the defendant, which did not have to be on reasonable grounds, that the victim was 14 or over. The House of Lords found that mens rea is an essential ingredient unless Parliament has indicated a contrary intention either expressly or by necessary implication.