Alternative Suspect Evidence
Generally, the accused is permitted to adduce evidence tending to establish someone else as the culprit of the offence for the purpose of raising a reasonable doubt of their own responsibility.
When considering alternative suspect evidence (also referred to as third party evidence), it is not for the trier-of-fact to determine if the alternate suspecte is the culprit. Only whether the "possible involvement of a third party raises a reasonable doubt" about the guilt of the accused.
R v McMillan (1975), 23 CCC (2d) 160 (C.A.), affd 1977 CanLII 19 (SCC),  2 SCR 824 per Martin J.A. at p. 757
R v Grandinetti, 2005 SCC 5 (CanLII),  1 SCR 27, at para 46
This is sometimes known as "Third Party Suspect" or "Alternate Suspect" evidence
R v Khan, 2011 BCCA 382 (CanLII), 282 CCC (3d) 396, at para 91
R v Tomlinson, 2014 ONCA 158 (CanLII) at para 78
Raising the Defence
This type of evidence can only be raised where there is sufficient evidence to connect a third-party to the offence. This will turn on the question of sufficient relevancy and probative value. The alternative suspect must have sufficient provable connection to the offence and cannot simply be speculative. The evidence cannot simply be evidence of propensity or suggestive of a hypothetical motive. However, a specific propensity to commit a particular offence can be sufficient.
The evidence must nevertheless still comply with regular rules of evidence. This includes the requirement that the evidence be relevant and admissible on the issue of identity and establish "sufficient" connection between the third-party and the offence.
Air of Reality
Before the evidence can be considered, the accused must show that there is an air of reality to the defence of another suspect. There must be a basis upon which a properly instructed jury could acquit.
It is considered essential that the alternative suspect evidence have sufficient connection with the offence as "evidence of opportunity". Merely, providing disposition or motive evidence will not be sufficient to be admissible. As the regular rules dictate, charged offences cannot be used to infer disposition.
e.g. R v Grandinetti, 2005 SCC 5 (CanLII),  1 SCR 27
R v Labbe, 2001 BCCA 653 (CanLII), (2001), 159 CCC (3d) 529 (BCCA)
R v Arcangioli, 1994 CanLII 107 (SCC),  1 SCR 129
R v Shchavinsky, 2000 CanLII 16877 (ON CA) (2001) 148 CCC (3d) 400 (ONCA)
R v Aprile 2007 QCCA 1041 (CanLII)
R v Vanezis, 2006 CanLII 37954 (ON CA), (2006) 213 CCC (3d) 499 (ONCA)
R v Tomlinson, 2014 ONCA 158 (CanLII), at para 72
R v Williams, 1985 CanLII 113 (ON CA), (1985), 18 CCC (3d) 356 (Ont. C.A.), at p. 366, leave refused
Tomlinson, supra at para 73
McMillan (1975), 23 CCC (2d) 160 (C.A.), affd 1977 CanLII 19 (SCC),  2 SCR 824 per Martin J.A., at p. 757
Grandinett, supra, at para 46
Tomlinson, supra at para 74
Grandinetti, supra, at para 47
R v Spackman, 2012 ONCA 905 (CanLII), 295 CCC (3d) 177, at para 121
- R v Fontaine, 2004 SCC 27 (CanLII),  1 SCR 702, at para 70
- Tomlinson at para 75
Thomlinson, supra at para 75
Grandinetti, supra at para 48
Tomlinson, supra at para 77
See also Character Evidence
When raising alternate suspect evidence, the Crown is permitted to present reply evidence that it would not otherwise be allowed to adduce. Where evidence of an alternative suspect is raised, there is a risk that the trier of fact would be left with the wrong impression about the insufficiency of the investigation. Accordingly, the Crown will be permitted to lead evidence on the investigative process that includes hearsay and bad character evidence of the accused.
R v Dhillon (2002), 2002 CanLII 41540 (ON CA), 166 CCC (3d) 262 (ONCA) at p. 277
Form of Evidence
The presentation of alternative suspect evidence of disposition may be established by way of expert disposition evidence or by propensity evidence from a prior criminal record.
Evidence of the accused's prior record and the circumstances surrounding them will only be available in limited circumstances.
- e.g. see R v McMillan (1975), 23 CCC (2d) 160 (C.A.), affd 1977 CanLII 19 (SCC),  2 SCR 824 per Martin J.A.
Tomlinson at para 76
R v Arcangioli, 1994 CanLII 107 (SCC),  1 SCR 129, at p. 141
R v Dorfer, 2011 SCC 50 (CanLII), 2011 SCC 50,  3 SCR 366, at para 1
- e.g. R v Paul, 2004 CanLII 26339 (ON SC)
Inadequate Police Investigation
Alternate suspect evidence can include evidence that the police inadequately investigated alternate suspects.
If the accused is advancing an argument of inadequate police investigation, a voir dire should be held on the admissibility of the evidence. It is best practices that this voir dire be held before the the empanelling of a jury. The voir dire should also produce "a clear ruling to define the parameters and limits on this type of evidence and to ensure that the evidence will be led in an orderly manner that is fair to both sides".
Where the accused advances evidence of inadequate police investigation, the Crown must be permitted to rebut the allegations. It is for this reason that this type of defence is considered "risky" as it will open the scope of permissible Crown evidence.