In estimating the weight to be attached to a reproduction of a document admitted in evidence pursuant to this part, regard shall be had to the fact that, if the person making an affidavit pursuant to this part is not called as a witness, there has been no opportunity to cross-examine the person, and to all the circumstances from which any inference may reasonably be drawn as to—
(a) the necessity for making the reproduction or, in the case of a print from a transparency, the transparency or for destroying or parting with the document reproduced; or
(b) the accuracy or otherwise of the reproduction; or
(c) any incentive to tamper with the document or to misrepresent the reproduction.