Experts on forensic toxicology who were called by both the defence and the prosecutor agreed that she could have given consent despite her blackout. Dr Pieternel van Niewenhuijzen, the expert for the prosecution, explained that despite the loss of memory people experiencing blackouts “can have conversations, they can drive, they are capable of responding, as though perfectly normally, to external stimuli. …. the person so affected is still capable of functioning in ways that might appear to an observer to be completely normal…. Furthermore, a person in that state may be capable of masking outward signs of intoxication, such as psychomotor difficulties like walking unsteadily and slurred speech; all the more so in someone who is a seasoned drinker."

[...]

The accused men in these cases were found not guilty because of this vital principle. In addition, the judges awarded costs against the crown and made it clear these cases should never have ended up in court. Both cases attracted headlines and ultimately contributed to the decision by the Crown Prosecution office to hold an audit into whether sexual assault cases are being supported by unsatisfactory evidence. These

(1) Drunk sex and consent - Bettina Arndt

But all is not rosy:

Which brings me back to Michael Lee, the judge who made the recent decision, now under appeal, in the Bruce Lehrmann defamation case. Even though Bruce Lehrmann claimed no sexual activity took place, Justice Lee did not believe him and the case then turned upon whether the sex was consensual.

Lee found that Lehrmann raped Brittany Higgins, on the balance of probabilities. He believed her when she said she did not consent.