I am assuming that you are talking about consent as a defence, so as far as consent goes it is when the defendant can prove that they acted with consent from the victim. It is listed as a complete defence, and may be used in sexual assault cases but is not a defence for murder. Just be aware that in some cases consent will not acquit the defendant, it may only reduce liability. There is a bit on consent at this website: http://www.justd.com/notes2.htm
And, of course, the Crimes Act 1900 (NSW)http://www.austlii.edu.au/au/legis/nsw/consol_act/ca190082/s77.html
Hope this is helpful and that I wasn't just telling you things that you already know! All the best!