Six ways monastic offenses are committed:
1. unconscientiously, i.e., knowing that an action is contrary to the rules, but going ahead with it anyway;
2. unknowingly, i.e., not realizing that the action is contrary to the rules;
4. assuming something improper to be proper, e.g., drinking a glass of apple wine perceiving it to be apple juice;
5. assuming something proper to be improper, e.g., perceiving a glass of apple juice to be apple wine, and drinking it nonetheless; and
6. acting out of uncertainty, i.e., not being sure if an action is proper, but going ahead with it anyway. In this last case, if the action is improper, one is to be treated according to the relevant rule. If it is proper, one incurs a dukkata in any event for having acted irresponsibly.
(from Vinaya, Parivara IV. 7.4)
(Throughout the Vinaya rules for monks and nuns there are stories which demonstrate that intent must be present. For example, if someone forces an improper act on a monk or nun without their consent, there is no offense for the monk or nun. This insistence on intent was one of the notable features of the Buddha’s Vinaya, in contrast to some of the existing philosophies at the time of Buddha and compatible with modern jurisprudence that insists on mens rea, ‘criminal intent’ before there is a crime.)