in flagrante delicto
/ɪnfləˌgrænteɪdɪˈlɪktəʊ/( <非正式> 亦作in flagrante)
adverb
- in the very act of wrongdoing, especially in an act of sexual misconduct在作案（尤指奸情）现场, 当场：
he had been caught in flagrante with the wife of the Association's Treasurer.
他和协会财务主管的妻子被捉奸在床。
词源
Latin, 'in the heat of the crime' （literally 'in blazing crime'）.