The ACT's Justice and Community Safety committee will hold hearings over the next fortnight into a private members bill from Greens crossbencher Caroline Le Couteur 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.

Current laws include a list of factors that negate consent such as threats of violence, intoxication or cases of mistaken identity, but also state those who do not offer up physical resistance effectively consented to sex.

Ms Le Couteur said every Australian jurisdiction except the ACT has a statutory definition of consent based on the idea of free and voluntary agreement in an opinion piece for The Canberra Times in February.

However committee chair Elizabeth Lee said the issue of consent was one of "considerable concern" in the community.

The committee will consider whether the bill would reverse the onus of proof, and set the burden of proof too high.

The ACT Bar Association says while consent laws could be given greater clarity, the bill undermined the presumption of innocence.

"[The bill] would require the accused to prove that he/she was satisfied on reasonable grounds that the agreement was freely and voluntarily given," their submission said.

"This not only shifts the ultimate onus of proof to an accused but by the use of the expression 'satisfied' lifts the level of satisfaction from a lower threshold of 'belief'.

"Such an approach overthrows the general approach to criminal liability set out in the Crimes Act 1900 and Criminal Code 2002 (see section 58). It would also be contrary to the right to a fair trial set out in section 21 and of the Human Rights 2004 and the presumption of innocence found in section 22 of the Human Rights Act 2004 ."

However the ACT Council of Social Services said without a "yes means yes" model, ACT laws failed to protect victims who were unable or felt too unsafe to say no.

"The onus is on the victim/survivor to prove that they did not consent (i.e. through verbal or physical resistance), rather than that they did," the council's submission said.

"There is no reason someone who lives in Queanbeyan and works in Canberra should be afforded different protections at work and at home.

"Updating our consent legislation to be as protective as other states and territories will help safeguard the rights of these people."

The Women's Centre for Health Matters Inc said the changes represented a major shift in community attitudes towards what was accepted as consenting activity.

"Situations in which consent was not considered to be negated because the victim did not verbally state their non-consent should, with this change in definition, be considered a sexual offence," their submission said.

However the centre said there would still be situations where subjective decisions about whether consent was obtained may need to be made, like in the instance of "rape freeze".

"Women who may have actively consented prior to sexual activity beginning, may in fact find that the activity is not what they thought they were consenting to, and may experience 'rape freeze', in which they do not demonstrate ongoing consent, nor do they physically act to try and stop the activity," their submission reads.

"In this situation, it is not clear whether the new legal definition of active consent has been met. A woman might give consent, freely and voluntarily, before activity begins, and may not physically resist ongoing activity after she has realised she wants to withdraw consent because of rape freeze.

"An example that describes such a situation, and makes it clear that there is a legal obligation to check for ongoing active consent if the woman is not demonstrating this through her body language, would be helpful for the courts."

The NSW government is also reviewing consent laws after the high-profile acquittal of Luke Lazarus, who was accused of raping an 18-year-old woman in an alleyway behind his father's King Cross night club in 2013.

The woman at the centre of the case, Saxon Mullins, waived her anonymity to speak to the ABC's Four Corners about the need to reform consent laws.

A jury and judges found Ms Mullins did not consent to sex, but the legal sticking point has been whether Mr Lazarus knew she did not consent. 

The District Court acquitted Mr Lazarus after a retrial in 2017,  finding his belief in consent was reasonable.

The ACT inquiry will begin hearings on Friday.