In case of illegal Intercourse in Islam. If a person doesn't remember, uncertain, doubts or is unsure whether the action of penetration took place. Does the person still need to offer expiation or a sincere repentance made in past is enough?
It is not that the person was intoxicated rather it was long time ago. There was just touching or pressing of private parts. Since the ruling is only on tip of penis it is really hard to tell whether it penetrated or not if one didn't saw.