s.146 of the Evidence Act notes that:
- Where a document or thing is produced wholly or partly by a device or process, AND
- the device or process is one that, or is of a kind that, if properly used, ordinarily produces that outcome, THEN
- it is presumed (unless evidence sufficient to raise doubt about the presumption is adduced) that, in producing the document or thing on the occasion in question, the device or process produced that outcome.