Every accused has a constitutional right to hear Crown witnesses and have disclosure before testifying.
As a matter of common sense, there may be considerable force to the suggestion that a person who gets full advance notice of the other side’s evidence and testifies last is in a position to tailor his or her evidence to fit the disclosure.
Notwithstanding, an accused’s constitutional right to disclosure cannot be allowed to become a trap.
R. v. Marshall (2005), 2005 CanLII 30051 (ON CA), at para. 71.
As a general rule, the Crown is prohibited from alleging that an accused person has tailored his evidence after receiving Crown disclosure or after hearing the Crown’s evidence at the preliminary inquiry or at trial, absent evidence of recent fabrication. Such allegations are improper and unfair.
R. v. Peavoy, 1997 CanLII 3028 (ON CA).
Relatedly, it is also a general rule that the prosecutor’s cross-examination of an accused that is calculated to suggest to the jury that an accused’s testimony was suspect because she or he had received disclosure, knew the prosecution’s case and had not been asked to reveal her or his own case until testifying at trial is at once improper and potentially prejudicial.
R. v. White, 1999 CanLII 3695 (ON CA).
Improper cross-examination of an accused may taint a trial by causing actual prejudice to the accused or by creating the appearance of unfairness:
R. v. White.
However, while questions concerning disclosure are “always potentially dangerous”, not every reference to disclosure is necessarily impermissible.
R. v. White.
The prudent course whenever Crown counsel wish to cross-examine on matters relating to disclosure is to vet the proposed line of questioning with the trial judge in the absence of the jury.
R. v. White.
Trial counsel for the accused should be vigilant and object to any improper cross-examination on the use of disclosure, as on appeal the failure of trial counsel to object can afford some indication that counsel did not consider the cross-examination unfair or prejudicial.
R. v. F.E.E., 2011 ONCA 783 (CanLII), at para. 77.
When Cross-examination is permissible
Whether cross-examination of an accused about his or her receipt of and familiarity with prosecutorial disclosure is permissible or improper depends on the circumstances of each case.
R. v. Thain, 2009 ONCA 223 (CanLII), at para. 24.
Some examples of circumstances in which cross-examination may be proper include the following:
· Accused brings an alibi defence
One instance in which it may be appropriate for a prosecutor to refer in cross-examination to an accused’s receipt of disclosure is to undermine a defence of alibi, thereby to contend that the accused has tailored his or her evidence to fit the Crown’s disclosure.
R. v. Thain, at para. 24; R. v. Khan, 1998 CanLII 15007 (BC CA),  B.C.J. No. 1450, 126 C.C.C. (3d) 523 (C.A.), at para. 50; R. v. Marshall (2005), 2005 CanLII 30051 (ON CA), 77 O.R. (3d) 81,  O.J. No. 3549 (C.A.), at paras. 74-75; and R. v. Simon, 2001 CanLII 11996 (QC CA),  J.Q. no 1328, 154 C.C.C. (3d) 562 (C.A.), at pp. 573-74 C.C.C.
· Accused uses Crown disclosure to corroborate his own evidence
Where the accused has suggested that records in the Crown disclosure confirm aspects of his testimony, it may be proper for the Crown to cross-examine on the fact that the accused received and reviewed the disclosure prior to trial so that his or her testimony can be viewed in that light:
Thain at para. 24; White at p. 768; see also R. v. Cavan and Scott (1999), 1999 CanLII 9309 (ON CA), 139 C.C.C. (3d) 449 (Ont. C.A.); R. v. Kokotailo, (2008), 2008 BCCA 168 (CanLII), 232 C.C.C. (3d) 279 (B.C.C.A.).
· Where there is evidence of recent fabrication.