Necessity Under the Principled Approach to Hearsay
Necessity must be in relation to a particular goal. The court should consider whether that goal can be achieved by other evidence that would otherwise be more reliable. If the exists other avenues of proving the fact sought then the exception will not apply.
- see eg. R v Abel, 2011 NLTD 173 (CanLII) at para 117
- See R v Devine, 2008 SCC 36 (CanLII) at para 16
R v U.(F.J.), 1995 CanLII 74 (SCC),  3 SCR 764
see also R v De Elespp  A.J. No. 6702 at paras 37 and 108
R v Rombough, 2006 ABPC 262 (CanLII),  A.J. No 1768 at para 36
R v Biscette  A.J. No. 557
R v Clarke (Ont. Ct. (Gen. Div.))  O.J. No. 997 at para F
- R v U(FJ), 1995 CanLII 74 (SCC),  3 SCR 764
Death of the witness is typically sufficient to establish necessity so long as the witness was the only source of information contained within the statement.
- e.g. R v Taylor, 2012 ONCA 809 (CanLII)
Dishonestly Forgetful Witness
A witness who falsely claims a lack of memory can often be identified by consideration of factors such as the amount of time that has passed since the observations and the selectivity of the memories remembered.
Where "truth is being held hostage" by the witness, it is functionally the same as a witness who refuses to testify, resulting in the necessity element being satisfied.
e.g. R v BRJ, 2012 NSPC 32 (CanLII) at para 21 to 24
BRJ, ibid. at para 24
Witness Refuses to Testify
A witness who refuses to testify when all efforts to obtain that testimony have been taken to no avail will typically satisfy the requirement of necessity.  There is no onus on the Crown to prove why the complainant failed to testify.
A witness who is shown to have refused to speak to the Crown or cooperate in any manner may amount to sufficient evidence to establish necessity.
R v Lavery, 1995 CanLII 2529 (BC SC),  BCJ No.2713 (S.C.), at para 9;
R v C.C.B., 1999 CanLII 12409 (SK PC),  S.J. No. 672 (P.C.), at paras 5 - 9, and 23 - 31
R v Goodstoney, 2005 ABQB 128 (CanLII)
R v Gardipy, 2012 SKCA 58 (CanLII) at para 19
R v Johnson, 2018 NSCA 64 (CanLII) at paras 162 to 182
Where the experience testifying may be so traumatic at to prevent a child from testifying, the requirement of necessity will be satisfied.
While in some limited cases the court may have the child testify within the voir dire to support the reliability of the statement. More often, the statement will be admitted without oral evidence and the lack of cross examination will go to the weight of the prior statement.
R v Rockey, 1996 CanLII 151 (SCC),  3 SCR 829 at p. 846
Sopinka, The Law of Evidence in Canada, 2nd edition, at ss.6.55