A useful reminder of the meanings of aiding, abetting, and wilful blindness has been given by the Supreme Court of Canada in R v Briscoe  SCC 13 (8 April 2010). Charron J, for the Court, noted that the actus reus of aiding is assisting or helping the principal offender, and abetting is encouraging, instigating, promoting or procuring the commission of the offence (para 14).
The definition of secondary liability in s 21(1)(b) and (c) of the Criminal Code will be familiar everywhere:
"21. (1) Every one is a party to an offence who
(a) actually commits it;
(b) does or omits to do anything for the purpose of aiding any person to commit it; or
(c) abets any person in committing it."
The mens rea element has two components: purpose or intention of assisting (which does not require a desire that the offence should be committed), and knowledge of the principal offender's intention to commit the offence (para 16, 17).
In some jurisdictions inciting, counselling, and procuring are included with aiding and abetting, but in Canada counselling is dealt with in s 22 of the Code and is defined there to include procuring, soliciting or inciting.
Wilful blindness is a substitute for actual knowledge. It is not the same as recklessness. It is a subjective state of mind: seeing the need for further inquiries but deliberately choosing not to make them. Wilful blindness could more aptly be called "deliberate ignorance" (para 20, 21, 24).
The Court in Briscoe approved Glanville Williams's description, in Criminal Law: The General Part (2nd ed, 1961) at p 159, of wilful blindness being equivalent to knowledge. This could be a little confusing, because if it is equivalent to knowledge, and if recklessness is the unreasonable taking of a known risk, then wilful blindness should constitute the knowledge required for recklessness. We are left clear on what wilful blindness is, but confused about why its distinction from recklessness is important. Williams was, as the passsage quoted at para 23 of Briscoe makes clear, concerned to distinguish wilful blindness from civil negligence (in relation to the failure to perceive what a reasonable person would have perceived). A negligent failure to be suspicious could not amount to wilful blindness, but - I suggest - recklessness involves an actual suspicion and could be wilful blindness. Acting in the face of a suspicion is not far removed from acting while not wanting to know if the suspicion is true.
These considerations prompt us to ask whether the mens rea for a secondary party should necessarily be stricter than that for a principal offender. However, no new law was established in Briscoe. The alleged secondary party had to know that the principal had the necessary state of mind to be guilty of the offence, and here the trial judge should have considered whether Mr Briscoe had been wilfully blind so as to have this knowledge imputed to him. The appeal was dismissed, so that the Court of Appeal's order for a retrial stood.