Greens crossbencher Caroline Le Couteur wants to introduce an affirmative consent model in the ACT that would define consent as "free and voluntary agreement" and require the accused to prove they knew or were "satisfied on reasonable grounds" that consent was freely given.

Currently, to prove a defendant is guilty of sexual intercourse without consent, prosecutors must prove four elements beyond a reasonable doubt - that the accused engaged in the act; that the act constituted sexual intercourse; that the complainant did not consent; and that the accused was reckless as to whether the complainant consented.

ACT Law Society criminal law committee chair Michael Kukulies-Smith told a Legislative Assembly inquiry on Tuesday Ms Le Couteur's bill conflated two separate issues - whether consent was given and whether the defendant reasonably believed it was - and he would struggle to explain it to a first-year law student.

Mr Kukulies-Smith said judges already spent between two and three hours explaining the legal tests to juries and "adding more law and more complexity is not simplifying that process".

"I would suggest making it more likely [jurors] will fall back on their own prejudices, their own gut instincts in relation to the case rather than the legal tests that are being espoused," Mr Kukulies-Smith said.

“Really the question is how is a judge going to explain this to a jury? If the jury can't understand, it doesn’t matter what the test is. If it becomes too convoluted for a jury to understand the test becomes irrelevant."

Mr Kukulies-Smith said raising the threshold from belief there was consent to being satisfied on reasonable grounds there was consent was a "high bar to get over" and would likely lead to a more "aggressive" cross-examination of victims.

This is because sexual assault cases rarely settle before trial, almost always result in jail time and are rarely supported by external evidence, meaning it often comes down to he-said, she-said, Mr Kukulies-Smith said.

"This runs the risk of ... necessitating an approach to the litigation by defendants that impresses the amount of attack that will be needed to get over that bar," Mr Kukulies-Smith said.

Mr Kukulies-Smith said the criminal law was the wrong instrument to enact social change, and suggested the ACT look at pursuing educational programs instead.

"Normative change through the law works when laws are simple and easily understood, so [for example] drugs are illegal, it’s an easy concept, it’s easy for people to know cocaine is a drug, ecstasy is a drug and it's easy for the jury to understand it is illegal to possess that drug, it’s illegal to sell that drug so the law can have a normative effect in that case," he said.

"The nuances of how sexual consent plays out in a bedroom is not something that is likely to be effectively changed by changes to the criminal law.

"[The criminal law] is an instrument to determine guilt or innocence in a courtroom. The criminal law is not an effective instrument to determine social policy, there are other instruments available that are nowhere near as blunt in that regard."

The inquiry also heard from Rape and Domestic Violence Services Australia's Kajhal McIntyre, who said sexual assault cases should be heard by judges only, who had specifically been trained in that area of law.

The idea stands in contrast to evidence provided from the ACT Director of Public Prosecutions Jon White, who suggested the result of the high profile Lazarus trial would have had a different outcome if it happened in the ACT, as all sexual assault cases must be trialled by jury.

Ms McIntyre said the presence of a jury in the courtroom could have a "harmful impact" on a victim and unlike judges, juries did not realise rationales for their decisions.

"As long as jurors are making decisions around these cases, we have no ability to recognise or correct misapplications of the law and because we know the law is so complex in this area, it's extremely important we do have that transparency," Ms McIntyre said.

The inquiry continues.