Mens rea
a guilty mind
Where the phrase comes from
The mental element of a criminal offence: intention, knowledge, recklessness, or, for some offences, negligence. It sits beside the act.
What lawyers are pointing at
Many crimes are not committed by a movement alone. The prosecution has to prove the state of mind the statute names. Some regulatory offences are strict, which means the mental element is thin or absent. A bad motive without the prohibited act is not the crime, and an accident without the required mind is not that crime either. The Latin does not mean 'someone feels guilty.'
The same shape in code
The diff is what happened. Mens rea is whether the author meant that result, knew the check was already red, or did not look. A postmortem that jumps from a broken build to a moral verdict has skipped the element the criminal law keeps separate on purpose.
A concrete picture
Taking a suitcase you believe is yours is not the same offence as taking a suitcase you know is not yours, even though the arm movement looks the same.