M. R. Evid. 405: Methods of proving character.

(a) Reputation or opinion. In all cases in which evidence of character or a trait of character of a person is admissible, proof may be made by testimony as to reputation or by testimony in the form of an opinion. On cross-examination, inquiry is allowable into relevant specific instances of conduct.

(b) Specific instances of conduct. In cases in which character or a trait of character of a person is an essential element of a charge, claim, or defense, or where the character of the victim relates to the reasonableness of force used by the accused in self defense, proof may also be made of specific instances of that person's conduct.