is low. When that threshold is satisfied, the electronic document is
admissible, and thus available for use by the trier of fact.
 To satisfy this modest threshold for authentication,
whether at common law or under s. 31. 1 of the CEA, the proponent may adduce and rely upon direct and circumstantial evidence. Section 31. 1 does not limit how or by what means the
threshold may be met. Its only requirement is that the evidence
be capable of supporting a finding that the electronic document
“is that which it is purported to be”. That circumstantial evidence may be relied upon is well established: Hirsch, at para. 18;
R. v. Colosie,  O.J. No. 1473, 2016 ONSC 1708 (S.C.J.), at
para. 25; R. v. Bulldog,  A.J. No. 813, 2015 ABCA 251, 326
C.C.C (3d) 385, at para. 35; see, also, R. v. Evans,  3 S.C.R.
653,  S.C.J. No. 115, at p. 663 S.C.R. This accords with general principles about proof of facts in criminal proceedings,
whether the facts sought to be established are preliminary facts
on an admissibility inquiry or ultimate facts necessary to prove
 At common law, correspondence could be authenticated by
the “reply letter” doctrine: to authenticate correspondence as
having been sent by one individual to another, evidence is
adduced to show it is a reply to a letter sent to that person. As a
matter of logic, the same should hold true for text messages and
emails. Evidence that A sent a text or e-mail to B whom A
believed was linked to a specific address, and evidence of a
response purportedly from B affords some evidence of authenticity:
David Paciocco, “Proof and Progress: Coping with the Law of
Evidence in a Technological Age” (2013), 11 C.J.L.T. 181, at pp.
 In a similar way, text messages may be linked to particular
phones by examining the recorded number of the sender and
receiving evidence linking that number to a specific individual, as
for example, by admission: Paciocco, at p. 198.
 But what of the prospect of tampering? Does it have to be
negated before digital evidence can be properly authenticated?
 As a matter of principle, it seems reasonable to infer that
the sender has authored a message sent from his or her phone
number. This inference is available and should be drawn in the
absence of evidence that gives an air of reality to a claim that this
may not be so. Rank speculation is not sufficient: R. v. Ambrose,
 O.J. No. 7234, 2015 ONCJ 813, at para. 52. And even if
there were an air of reality to such a claim, the low threshold for
authentication, whether at common law or under s. 31. 1 of the
CEA, would seem to assign such a prospect to an assessment of