Christine Hurt poses the titular question, explaining that:
Conscious avoidance, sometimes called "willful ignorance," or "willful blindness," has helped prosecutors get convictions against several high-profile white-collar defendants, including Bernard Ebbers, Ken Lay and Jeff Skilling. ... This theory, in the form of a jury instruction, allows jurors to find that defendants commited securities fraud with intent even absent proof of knowledge of the specific illegal acts if "the evidence would permit a rational juror to conclude beyond a reasonable doubt that the defendant was aware of a high probability of the fact in dispute and consciously avoided confirming that fact."
In addition to Christine's article on the subject, those interested should see David Luban, Contrived Ignorance, 87 Geo. L.J. 957 (1999), which is useful both for its survey of doctrine and its discussion of the moral blameworthiness of deliberate ignorance.