Author: Bill Doogue
Practice area: white collar 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 (State)?
Unauthorised Modification of Data to Cause Impairment (State) is a Victorian computer offence under section 247C of the Crimes Act 1958. It criminalises deliberate interference with computer-held data where a person tampers with digital information without authority in a way connected to disrupting how that data or system functions.
Key points
- Elements: An unauthorised modification of data, knowledge of that lack of authority, and intention or recklessness as to impairment.
- Conduct: Modifying computer data in a way that affects access, reliability, security or operation.
- Court: Indictable offence heard in the County Court unless dealt with summarily in the Magistrates’ Court.
The maximum penalty for Unauthorised Modification of Data to Cause Impairment (State) is 10 years imprisonment.
Common defences may include factual dispute, authorisation to make the modification, or absence of the required intent.
Have you been accused of Unauthorised Modification of Data to Cause Impairment – State?
Police Interview
There is usually nothing to be gained from making a comment in a Police interview. The Police are trained in interview techniques that encourage you to reveal information that only assists their case. The Police are interested in strengthening their case, not in assisting you build your defence.
Pleading Not Guilty
If you are pleading not guilty to a charge of Unauthorised Modification of Data to Cause Impairment, your matter will likely go to a trial where the evidence will be tested.
Our lawyers go to Court every single day and contest all driving matters. Our lawyers know how to pick apart a weak prosecution case and are expert cross examiners of witnesses. We may be able to do investigations of our own on your computer using adequately qualified experts to re-construct what happened.
Pleading Guilty
If you are pleading guilty it is important that you engage an expert criminal defence lawyer to make a plea on your behalf. A thoughtful plea can ensure that you have the best chance at receiving the minimum penalty for this offence. There is normally a lot of work to be done prior to the plea hearing in negotiating the agreed summary and prepare a plea strategy. You want the best lawyer in your corner representing you in Court.
Which court will the case be heard in?
This is an indictable offence which means that it will be heard in the County Court, unless heard summarily in the Magistrates’ Court.
Examples of Unauthorised Modification of Data to Cause Impairment (State)
- You are highly skilled with technology and decide to modify a local business’ data system to allow yourself access to information about their customers. You later use this information to siphon cash from the customers’ bank accounts.
What is the legal definition of Unauthorised Modification of Data to Cause Impairment (State)?
A person who—
- causes any unauthorised modification of data held in a computer; and
- knows that the modification is unauthorised; and
- intends by the modification to impair access to, or to impair the reliability, security or operation of, any data held in a computer or is reckless as to any such impairment—
is guilty of an offence.
Legislation
The legislation for this offence can be found on section 247C of Crimes Act 1958.
Elements of the offence
To prove this charge the Prosecution must prove the following beyond reasonable doubt:
- The accused caused any unauthorised modification of data held in a computer; and
The modification must be unauthorised. For example, many businesses authorise IT consultants to modify their data. However, if an IT consultant was acting outside their contract and without permission, this would be unauthorised. - The accused knew that the modification was unauthorised; and
The accused must be aware that the modification was unauthorised. Whether or not the accused was aware will be determined by looking at the surrounding circumstances. - The accused intended, by the modification to impair access to, or to impair the reliability, security or operation of, any data held in a computer or was reckless as to any such impairment
The accused must have either intended that the modification would impair the data or have been reckless as to this consequence. Thus, mere inadvertence or carelessness would not be enough – there needs to be a positive state of mind.
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 ring us and discuss your case 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 cause any unauthorised modification of data held in a computer?
- Did you know that this was unauthorised?
- Did you intend to impair access to, or to impair the reliability, security or operation of, any data?
- Were you reckless as to any impairment?
Maximum penalty for section 247C of the Crimes Act 1958
A person proven guilty of having committed Unauthorised Modification of Data to Cause Impairment (State) (s247C of the Crimes Act 1958) may be sentenced to a maximum of 10 years imprisonment.
