Unauthorised Impairment of Data

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.

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Bill authored this content and last revised it for accuracy on 7 August 2026.

What is the offence of Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device?

This Victorian offence under Section 247H of the Crimes Act 1958 targets deliberate interference with electronically stored information where a person tampers with or disrupts data stored on a computer disk, credit card or similar device without lawful entitlement. It focuses on intentional digital interference affecting stored electronic data.

Key points

Elements: Causing unauthorised impairment of data, knowing it was unauthorised, and intending to cause the impairment
Conduct captured: Interfering with the reliability, security or operation of electronically stored data
Court: Summary offence heard in the Magistrates’ Court

The maximum penalty for Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device is level 7 imprisonment (2 years).

Common defences may include factual dispute, lawful authorisation, or duress.

Have you been accused of Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device?

Police Interview

If police suspect you have committed the offence of Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device, they are going to contact you to arrange an interview. Ensuring you obtain legal advice prior to going ahead with the interview is crucial.

At Doogue + George Defence Lawyers we have experience in dealing with criminal allegations from start to finish, we understand how a police interview can impact the running of your case in Court. Calling us prior to an interview will help you to feel more at ease in a daunting situation and ensures that you do not walk away from the police interview having compromised your position.

We will guide you through the interview process, discuss the likely questions and ensure you understand your rights and obligations including making a no comment interview or answering police questions.

Pleading Not Guilty

If you deny an allegation of Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device, you will take your matter to trial. One of our expert trial lawyers can help you to understand the Court process and the steps it will take to reach an acquittal in your case. Also, our lawyers will prepare to strongly defend your case. This will involve looking for failings in the brief of evidence and engaging an aptly qualified expert. In a case like this, there may be forensic evidence which needs to be analysed and explained to the jury.

Pleading Guilty

A plea hearing is your chance to tell the Court why you committed the offence of gaining Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device. The Court will want to hear about the circumstances that lead to the offending, your personal circumstances and legal submissions. Our lawyers are dedicated Court advocates and are best placed to represent you on a plea of guilty. Obtaining advice from Doogue + George Defence Lawyers will help to ensure you do not miss an opportunity to minimise the penalty.

Which court will the case be heard in?

This charge is a summary offence and will therefore be heard in the Magistrates’ Court.

Examples of Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device

You impair data held on a computer disk in order to give yourself access to a person’s private information.

What is the legal definition of Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device?

A person who—
1. causes any unauthorised impairment of the reliability, security or operation of data held on a computer disk, credit card or other device used to store data by electronic means; and
2. knows that the impairment is unauthorised; and
3. intends to cause the impairment—
is guilty of an offence.

Legislation

The legislation for this offence can be found on section 247H of Crimes Act 1958.

Elements of the offence

To prove this charge, the prosecution must prove the following beyond reasonable doubt:

The accused causes any unauthorised impairment of the reliability, security or operation of data held on a computer disk, credit card or other device used to store data by electronic means; and
According to section 3, impairment of reliability, security or operation of data is unauthorised if the person is not entitled to cause the impairment.
The accused knew that the impairment is unauthorised; and
The accused must have known that they were not entitled to cause the impairment. If the prosecution can’t show that the accused had knowledge, this offence will not be made out. Whether or not the accused knew they weren’t authorised will depend on circumstances.

Can they prove you knew the impairment was unauthorised?

The accused intended to cause the impairment
There must be an intention to cause the impairment. Mere inadvertence or carelessness will not be sufficient.

Defences

Defences to this charge can include can include a factual dispute, the fact that the accused was authorised, or duress.

You should ring us and discuss your case if you have been charged. Deciding on whether to plead guilty or not has implications for you and should be made after proper discussions with a criminal lawyer.

Questions in cases like this

Did you impair data?
Did you know that you were not authorised to impair the data?
Did you intend to cause the impairment?

Maximum penalty for section 247H of the Crimes Act 1958

The offence of Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device (s247H of the Crimes Act 1958) carries a maximum penalty of level 7 imprisonment (2 years).

FAQ About Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device

Does accidental damage to digital data amount to this offence?

No. The offence requires a deliberate act carried out with the intention of causing the impairment. Mere inadvertence or carelessness is not enough to establish criminal liability for unauthorised impairment of data.

What does “unauthorised” mean in a data impairment charge?

Conduct is unauthorised where the person is not entitled to cause the impairment. A person who has lawful authority or entitlement to interfere with the data will not satisfy this element of the offence.

Does this offence apply only to computers?

No. It extends beyond computers to data stored on a credit card or any other device used to store data electronically. The focus is on electronically stored data, not just traditional computer systems.

Is a genuine belief of having permission relevant to the charge?

Yes. The prosecution must establish that the accused knew the impairment was unauthorised. A genuine belief that they were entitled to interfere with the data is relevant to whether this mental element can be proven.

Can duress be relied on as a defence to unauthorised data impairment?

Duress is identified as a potential defence. It may arise where a person engaged in the conduct because of serious threats or pressure that meet the legal requirements for duress.

What types of issues are commonly contested in these cases?

Common issues include whether the impairment actually occurred, whether the accused was authorised, and whether the required knowledge and intention can be proven beyond reasonable doubt.

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Unauthorised Impairment of Data Held in Computer Disk, Credit Card or Other Device

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