Wilful Blindness - what does it mean?

One of our readers D wrote to me today:

One thing strikes me between the eyes about all this.
When Rupert faced the inquiry in Britain he was asked about phone hacking and if he knew and if not why not?
To which he said he knew nothing. No one told him!
He was then asked if he knew of the legal term "wilful blindness",
In other words - don't tell me your doing something wrong because then I can say I don't know and can't be blamed.

It's a serious charge for a director etc or in this case Rupert.

If that applies in Australia then surely wilful blindness at least should be put to Gillard.
She may not have "known" or wasn't  told by wilson because she simply didn't want to know so she could say that exact reason every time is probed about it.

Keep up the good work,  

Nick Styant-Browne has  this about Ms Gillard, ''For what my view is worth - and I have tried to avoid expressing my view and  just stuck to the facts - but I think at the very minimum she was wilfully  blind.''

Given that D asked about it, here's a report from the UK's The Guardian about wilful blindness.