Answer:
D. Stare Decisis.
Step-by-step explanation:
Stare Decisis refers to a legal doctrine in which the courts adhere to the precedents that are set by the last decisions. It adheres the prior cases and on the same time it also make a rule on the same case.
Since in the given situation, the criminal defendants in the past period has shown the defense in the same cases so the judge applied the Stare Decisis to figure out that is defense is available to him or not
Therefore the correct option is D.