http://www.cbc.ca/canada/story/2010/04/08/supreme-appeal.html

Wilful blindness refers to the mental state of a person whose suspicions are aroused but who abstains from making inquiries in order to avoid gaining actual knowledge of  incriminating facts. Until now this notion has been applied almost exclusively to impute knowledge of pre-existing facts in cases of illegal possession. For example, a person buying an item at an unusually low price from a person not normally dealing in such items can be found guilty of possessing stolen goods on the basis that the buyer kept themself wilfully blind as to the illegal nature of the goods by not wanting to know where they came from.

In the case referred to in the above article the Supreme Court has extended the doctrine by holding that a person can also be held liable for violent crimes by participating in events  they should know are leading up to illegal acts. In the case in point the Court decided the driver of a car in which the victim and several actual perpetrators were taken to a place where gruesome crimes were were committed some distance from the car in which the driver remained could be found guilty of those crimes without evidence of being specifically told by the actual perpetrators what they intended to do to the victim . It was held that if the circumstances apparent to the accused made it obvious serious crimes would be committed at the place to which he drove the others his actions could be considered as aiding in the commision of the of the offences, thus making him as guilty as those who actually committed them.