Final answer:
According to the MPC, evidence of Mental Disease or Defect is admissible when it is relevant to an element of the offense.
Step-by-step explanation:
According to the Model Penal Code (MPC) Section 4.02(1), evidence of Mental Disease or Defect is admissible when it is relevant to an element of the offense. This means that evidence of mental disease or defect can be used to establish that the defendant did or did not possess the necessary mental state required for a particular offense. However, it is important to note that mental disease or defect evidence does not automatically establish insanity as a defense.