Is failure to register as a offender considered a "strict liability" offense?

I have a friend who is a registered offender in Michigan (Romeo and Juliet relationship). He recently pled guilty to failure to register as a offender because he has a terrible time remembering dates and times, let alone what month it is. My question is, if he were to have fought the charge of failing to register, is a "strict liability" offense where the prosecutor would need only prove that the defendant was indeed late to register, or could there be a Mens Rea defense where he actually did not intend to forget to register?