Most juridical systems contain the principle that an act is only unlawful if the agent conducting the act has a ‘guilty mind’ (‘mens rea’). Different law systems distinguish different modes of mens rea. For instance, American law distinguishes between ‘knowingly’ performing a criminal act, ‘recklessness’, ‘strict liability’, etc. I will show we can formalize several of these categories. The formalism I use is a complete stit-logic featuring operators for stit-actions taking effect in ‘next’ states, S5-knowledge operators and SDL-type obligation operators. The different modes of ‘mens rea’ correspond to the violation conditions of different types of obligation definable in the logic.