The burden of proof that the case of accused comes within exception is on the 

Section 105 of Evidence Act Burden of proving that case of accused comes within exceptions. ––When a person is accused of any offence, the burden of proving the existence of circumstances bringing the case within any of the General Exceptions in the Indian Penal Code (45 of 1860), or within any special exception or proviso contained in any other part of the same Code, or in any law defining the offence, is upon him, and the Court shall presume the absence of such circumstances. Illustrations (a)  A, accused of murder, alleges that, by reason of unsoundness of mind, he did not know the nature of the act. The burden of proof is on A.