Burden of proving fact especially within knowledge
108.  When any fact is especially within the knowledge of any person, the burden of proving that fact is upon that person.
Illustrations
     (a)  When a person does an act with some intention other than that which the character and circumstances of the act suggest, the burden of proving that intention is upon that person.
     (b)  A is charged with travelling on a railway without a ticket. The burden of proving that A had a ticket is on him or her.