8.— In proceedings for an offence under this Act, where a person has stockpiled, acquired, possessed or retained or transferred to another person, or attempted to stockpile, acquire, possess or retain or transfer to another person, a microbial or other biological agent, or toxin (whatever its origin or method of production), of such a type and in such a quantity that it is reasonable to conclude that it has been developed or produced or is intended to be used for a hostile purpose—

(a) the agent or toxin is presumed to have been so developed or produced or to have been so intended, and

(b) the person is presumed to have known or been reckless as to whether or not it has been so developed or produced or was so intended,

unless the court or jury, as the case may be, is satisfied, having regard to the whole of the evidence, that there is a reasonable doubt that the agent or toxin was so developed or produced or so intended or the person so knew or was so reckless.