There were more than 15 convictions for rape set aside on appeal between 2010 and 2013 because judges had given directions to juries that were based on an incorrect interpretation of consent, the report said. One of these cases involved a 41-year-old man who had been found guilty of raping a 14-year-old girl, after a friend of the man had injected the girl with speed and given her alcohol, in an incident described by a judge as "exploitation of the worst kind". A new sex abuse offence, known as a course of conduct charge, has been introduced to prosecute offenders who are alleged to have abused victims on a number of occasions, often over many years. The Department of Justice review found that it was "not possible to quantify the degree of injustice wrought by the failure of the law to respond to repeated and systematic child sexual abuse", and found the new charge would help correct this injustice. Under current law, if a victim cannot remember details about the date of the offence, for example, it can be difficult for police to charge the alleged offender with each sexual act.

Police will be able to use the course of conduct charge – which is based on a United Kingdom model but is the first of its kind in Australia – if it can be proven there was a pattern, or history, of an offender abusing a victim. "It is not known how many complainants have their evidence rejected, either by police, prosecutors or judges, as being insufficiently particular for the purposes of a trial," the 2013 review found. Victoria Police Detective Senior Sergeant Mick Phyland said victims who made the difficult decision to report their abuse could be easily confused by the legal process, especially if an alleged offender was not charged because of a lack of evidence, or if that alleged offender walked from court because of a technicality. He said that victims of historic sexual abuse often wrestled with the decision to report a crime for years. "The impact that crimes have on people can sometimes influence their ability to recall, not only that but because of the passage of time records can be lost.

"The judicial process, particularly in relation to sexual assaults, can sometimes be daunting. "For all those involved, but particularly victims, having a simplified process and having these charges available could help." The reforms, which will become law on Wednesday, address concerns that a similar overhaul in 2007 had not done enough to make the justice system fair for victims of sexual abuse. There were 2067 rapes recorded by police in 2012-13, for example, but only 47 people sentenced for rape the following year. The review found that complexities in rape law were the main reason that appeals of rape convictions were successful.

The new definition of consent – which will apply to all sexual assault offences, not just rape – means that an offender must prove that if they believed a victim was consenting, that belief was not unreasonable. In simple terms, the change will mean an offender cannot argue that a victim consented because they did not say "no". It is believed a marketing campaign explaining the changes is being considered. The campaign would be based on those used in other jurisdictions that made similar changes to the definition of consent. "The existing rape laws are highly complex and difficult to explain to juries," says the report. "As a result, they have been the subject of numerous appeals and retrials, which are extremely stressful for victims/survivors, create delays in the criminal justice system and are costly."

Other changes include introducing an offence of sexual assault, to replace the offence of indecent assault, and the scrapping of time limitations which prevented the prosecution of certain sexual offences alleged to have been committed against children before 1991. The Crimes Amendment (Sexual Offences and Other Matters) Bill also clarifies sexting legislation, in a bid to prevent teens who consensually share images from being placed on the sex offenders register, and introduces a new grooming for sexual conduct offence. Centres Against Sexual Assault spokeswoman Carolyn Worth said there had been a wide consultation process as part of the overhaul, and victim support groups backed the changes. Under the changes to sexual offence laws: An alleged offender must have a "reasonable" belief that a victim had consented. The new definition means the defendant must detail the steps they have taken to find out whether the victim has consented.

A new course of conduct charge can be used when it is alleged that an offender has abused a victim on multiple occasions over an extended period, but specifics about each offence cannot be recalled

Exceptions to child pornography offences to prevent sexting teens being added to the sex offenders register

Removal of a time limitation that prevented prosecution for some child sex offences committed before 1991