Author: Bill Doogue
Practice area: Commonwealth offences
Bill is a founding Director of Doogue + George, ranked by Doyle's Guide as a Preeminent Criminal Defence Lawyer in Victoria (2026) and an LIV Accredited Criminal Law Specialist since 1998 with over 30 years of experience in complex criminal and corporate matters. His depth of experience in this area means clients receive accurate, considered advice.
View full profile →Bill authored this content and last revised it for accuracy on 7 August 2026.
What is the offence of Unauthorised Modification of Data to Cause Impairment (Commonwealth)?
This Commonwealth cybercrime offence under section 477.2 of the Criminal Code Act 1995 (Cth) targets deliberate interference with computer data connected to the Commonwealth. It applies where a person tampers with data in a way that disrupts or undermines the proper functioning of a computer system or the integrity of its stored information.
Key points
- Legal elements: Causing unauthorised modification of data, knowing it was unauthorised, with intent or recklessness as to impairment.
- Type of conduct: Deleting or removing data so as to impair access, reliability, security or operation of computer data.
- Court: Heard in the County Court before a judge and jury.
The maximum penalty for Unauthorised Modification of Data to Cause Impairment (Commonwealth) is 10 years imprisonment.
Common defences may include factual dispute, authorisation, or absence of the required intent.
Have you been accused of Unauthorised Modification of Data to Cause Impairment? If you have, you will want to discuss this allegation with an experienced criminal defence lawyer who can give you strategic advice. Get in contact with us immediately after becoming aware of the allegation to make an appointment with one of our lawyers.
Police Interview
Your defence to an allegation of Unauthorised Modification of Data to Cause Impairment begins at your first interaction with Police. It is important to understand that there is no such thing as an ‘off the record’ discussion and anything you tell the Police will appear in evidence against you if they think it helps their case against you.
The Police interview is not the place for you to explain your side of the story and hope the matter will go away. The Police will want to interview you because they have decided that you are guilty of Unauthorised Modification of Data to Cause Impairment and they want to try to get admissions from you.
Our lawyers can prepare you for your interview to make sure you do not say anything which will make defending the charge in Court more difficult later on. It is worth remembering that Police officers are trained to ask questions in a way to make you look like you are not telling the truth. Therefore, it is best not to say anything during the interview you are not required to say.
You can always provide the Police with a statement after the interview which will explain the full circumstances if you have a defence.
Also these crimes are incredibly hard to prove with the reality being that people can remotely access computers and also plant evidence.
Our lawyers can also attend the Police station with you and sit in on the interview to make sure you do not say something you don’t have to. It is comforting to have someone in the interview who is on your side.
Pleading Not Guilty
If the Police charge you with Unauthorised Modification of Data to Cause Impairment, you will understandably feel stressed and want to speak with someone who can answer your important questions. You should get in touch with our firm and make a time to have a private and confidential conference to ask your questions. Our lawyers are unique because they approach matters with a view of securing evidence, speaking to potential witnesses and engaging appropriately trained experts. In a case of Unauthorised Modification of Data to Cause Impairment, it is worthwhile engaging an expert who can secure data from your computer which may exonerate you. Our lawyers have a lot of experience in defending allegations of computer based crime that we use to your advantage in your case. Our lawyers know what works.
We also have in-house barristers who run our contested hearings and trials. They get involved in matters early on to develop a defence strategy.
Pleading Guilty
If you decide to plead guilty Unauthorised Modification of Data to Cause Impairment, one of our experienced lawyers can represent you in Court on a plea of guilty to get the best possible outcome for you. What we have discovered over decades of representing people in pleas of guilty is that preparation before Court is more valuable than what is said in the Court room. Our lawyers pride themselves on working closely with clients months and weeks ahead of their plea hearing to make sure that they gather enough mitigating material to get a good outcome.
Often these offences are committed by people who have got a bit lost in front of their computers and it is about getting the right evidence to prove this.
Which court will the case be heard in?
This offence is heard in the County Court before a judge and jury.
Examples of Unauthorised Modification of Data to Cause Impairment (Commonwealth)
- Sending a virus to a government body’s computer intending to cause an impairment.
What is the legal definition of Unauthorised Modification of Data to Cause Impairment (Commonwealth)?
Section 308A of the Commonwealth Code defines ‘modification’ of data as deleting and/or removing data.
Legislation
The legislation for this offence can be found on section 477.2 of Criminal Code Act 1995.
Elements of the offence
To prove this charge the Prosecution must show that the accused:
- caused a modification of data held in a computer,
- that the accused knew the modification was unauthorised,
“Can the Prosecution prove that the modification was unauthorised?”
- that the accused intended to or was reckless as to impairing access to or impairing the reliability, security or operation of any data held in a computer,
- The data that is modified must either be held in a Commonwealth computer or held on behalf of the Commonwealth in a computer.
Defences
Defences to this charge can include can include a factual dispute, the fact that the accused was authorised, or a lack of intent.
You should call us and discuss your case with one of our criminal defence lawyers if you have been charged. Deciding on whether to plead guilty or not has huge implications for you and should be made after proper discussions with a criminal lawyer.
Questions in cases like this
- Did you have authority to modify the data?
- Did you intend to cause an impairment to the data system?
- Did you in fact modify data?
- Did your modification cause the impairment?
Maximum penalty for section 477.2 of the Commonwealth Criminal Code 1995
The offence of Unauthorised Modification of Data to Cause Impairment (Commonwealth) (s477.2 of the Commonwealth Criminal Code 1995) carries a maximum penalty of 10 years imprisonment.
Case studies related to Unauthorised Modification of Data to Cause Impairment (Commonwealth)
