Mens rea usually means intent to do the thing, not intent to commit a crime.
E.g. if I involuntarily swing my arm and hit someone in the face as a result of a medical condition I lacked the appropriate mens rea and am not guilty. If I intentionally punch someone in the face while being somehow unaware that I'm not allowed to do that I am guilty.
Hard to see how mens rea would save anyone from being guilty here.
