Why dual criminality matters in UK extradition cases

Dual criminality is one of the fundamental safeguards in extradition proceedings. In most cases, a person can only be extradited from the UK if the conduct alleged by the requesting state would also amount to a criminal offence under UK law. Although the legal terminology may differ between countries, the court examines whether the underlying conduct would constitute an offence if it had occurred in the relevant part of the United Kingdom.

This principle continues to play a significant role in extradition proceedings under the Extradition Act 2003 and has become increasingly important in cases involving international financial crime, cybercrime and cross-border investigations.

What is dual criminality in extradition?

Dual criminality is a legal principle requiring that the conduct for which extradition is sought is criminal in both the requesting country and the requested country.

In the United Kingdom, this requirement is contained within the Extradition Act 2003. Depending on whether the request concerns a Category 1 or Category 2 territory, the relevant provisions require the court to consider whether:

“the conduct would constitute an offence under the law of the relevant part of the United Kingdom if it occurred in that part of the United Kingdom.”

The focus is therefore on the conduct itself, rather than the precise wording or legal classification of the foreign offence.

For example, if another country criminalises conduct that is entirely lawful in the UK, extradition may not be available because the dual criminality requirement would not be satisfied.

Similarly, where allegations involve complex financial crime, fraud, market manipulation or cyber offences, the court will assess whether the alleged behaviour would amount to an equivalent offence under UK criminal law, even if the foreign offence has a different name or contains different legal elements.

Why is dual criminality an important safeguard?

The principle protects individuals from being extradited for conduct that Parliament has not chosen to criminalise within the UK.

It reflects an important aspect of international cooperation by balancing two competing objectives:

• enabling countries to investigate and prosecute serious criminal offences;
• protecting individuals from extradition where the alleged conduct would not amount to criminal behaviour under UK law.

The principle also promotes legal certainty by ensuring that individuals are not surrendered solely because another country has adopted broader or fundamentally different criminal laws.

As international investigations increasingly involve multiple jurisdictions, dual criminality remains one of the key legal issues considered by UK courts in extradition proceedings.

How do UK courts determine whether dual criminality exists?

The court does not decide whether the requested person is guilty of the alleged offence.

Instead, it considers a narrower legal question:

If the alleged conduct had taken place in the relevant part of the UK, would it amount to a criminal offence?

Importantly:

• the foreign offence does not need to have the same legal name as the UK offence;
• every statutory element does not need to be identical; and
• the court compares the underlying factual conduct rather than the legal label attached by the requesting state.

This conduct-based approach has been confirmed by the UK courts in several important extradition decisions and remains central to modern extradition law.

Why identical offences are not required

One common misconception is that both countries must criminalise exactly the same offence.

This is not the case.

The UK court looks beyond the wording of the legislation and instead considers whether the alleged behaviour would amount to criminal conduct under UK law.

For example:

• fraud offences may be described differently across jurisdictions;
• financial market offences may have different statutory definitions;
• cybercrime legislation may vary considerably between countries.

Provided the underlying conduct would constitute a criminal offence in the UK, the dual criminality requirement may still be satisfied.

This approach enables extradition arrangements to function effectively despite significant differences between national criminal justice systems.

How dual criminality affects extradition proceedings

Whether the dual criminality requirement is satisfied can have a significant impact on the outcome of an extradition request. If the requesting state cannot demonstrate that the alleged conduct would amount to an offence under UK law (subject to any applicable statutory exceptions), extradition may not be permitted.

The issue commonly arises in cases involving:

• financial crime and fraud;
• cybercrime and computer misuse;
• corruption and bribery allegations;
• tax offences;
• sanctions-related offences; and
• offences involving differing standards of criminal liability across jurisdictions.

As international cooperation between law enforcement authorities continues to increase, requests involving complex cross-border conduct are becoming more common. Establishing whether the conduct satisfies the UK criminal law test is therefore often a key aspect of the defence strategy.

Does dual criminality always apply?

Not always.

Whether dual criminality must be established depends on the applicable extradition arrangements and the legal framework governing the request.

Following the UK’s departure from the European Union and the replacement of the European Arrest Warrant system with the UK-EU Trade and Cooperation Agreement (TCA), dual criminality has once again assumed greater importance in extradition requests between the UK and EU Member States.

Unlike the previous European Arrest Warrant framework, which removed the requirement for dual criminality in relation to certain categories of offences, the current arrangements generally require UK courts to consider whether the conduct would also constitute an offence under UK law, subject to the provisions of the Trade and Cooperation Agreement and domestic legislation.

For extradition requests from many non-EU countries, dual criminality has long remained a central legal requirement under the Extradition Act 2003.

Can INTERPOL be involved before extradition proceedings?

Yes. In many cases, an extradition request is preceded by international police cooperation through INTERPOL.

For example, a requesting state may seek the publication of an INTERPOL Red Notice or another international alert to locate an individual before commencing formal extradition proceedings. However, this is not a legal requirement.

An individual may:

• be subject to an INTERPOL Red Notice without any extradition request having yet been made;
• face extradition proceedings without ever being the subject of an INTERPOL Red Notice; or
• challenge an INTERPOL notice separately from defending extradition proceedings.

Although INTERPOL procedures and extradition proceedings are closely connected in many cases, they remain legally distinct processes requiring different legal strategies.

These resources explain how INTERPOL measures interact with international extradition proceedings and the options available to individuals facing cross-border enforcement action.

Common misunderstandings about dual criminality in extradition cases

Individuals facing extradition proceedings often misunderstand how the dual criminality test operates. Assuming that the foreign offence must be identical to a UK offence, or believing that the UK court will determine guilt or innocence at this stage, can result in an ineffective legal strategy.

Some of the most common misconceptions include:

• believing that the name of the offence must be the same in both jurisdictions;
• assuming that different legal definitions automatically prevent extradition;
• confusing the dual criminality assessment with the evidence required to prove the alleged offence;
• overlooking that some extradition arrangements contain statutory exceptions to the dual criminality requirement; and
• delaying specialist legal advice until formal extradition proceedings have already begun.

Because extradition cases frequently involve multiple jurisdictions and differing legal systems, obtaining legal advice at the earliest opportunity can be critical to identifying potential grounds for challenge.

Gherson insight

Dual criminality is often one of several complex issues that arise during extradition proceedings. In practice, its application may require a detailed analysis of the alleged conduct, the criminal law of both jurisdictions, and the relevant extradition framework.

At Gherson, we regularly advise individuals facing complex cross-border investigations, extradition requests and related INTERPOL matters. Our experience includes cases involving allegations of financial crime, politically sensitive prosecutions and parallel asylum proceedings, where extradition forms only one part of a broader international legal strategy.

Because extradition proceedings frequently involve overlapping issues across multiple jurisdictions, obtaining specialist advice at an early stage can help identify available legal protections and ensure that an appropriate defence strategy is developed from the outset.

Frequently asked questions

What does dual criminality mean in extradition?

Dual criminality means that the conduct for which extradition is sought must also amount to a criminal offence under UK law, subject to any applicable statutory exceptions. The court compares the underlying conduct rather than the exact legal wording of the offence.

Does the offence have to be identical in both countries?

No. UK courts do not require the offences to have the same name or identical legal elements. The key question is whether the alleged conduct would constitute a criminal offence if it had occurred in the relevant part of the United Kingdom.

Does dual criminality apply in every extradition case?

Not necessarily. Whether the requirement applies depends on the applicable extradition arrangements, including the Extradition Act 2003 and any relevant international agreements. Some statutory exceptions may apply in particular circumstances.

Can I challenge extradition on the basis of dual criminality?

Potentially. If the alleged conduct would not amount to a criminal offence under UK law, or if the legal requirements have not been satisfied, dual criminality may form part of an extradition defence. Each case depends on its own facts and the relevant legal framework.

Is an INTERPOL Red Notice the same as an extradition request?

No. An INTERPOL Red Notice is a request to locate and provisionally detain an individual and is not itself an extradition request or an international arrest warrant. Formal extradition proceedings are separate legal processes, although the two are often connected.

Readers interested in this topic may also find our related articles helpful:

• How to remove an INTERPOL Red Notice: a complete legal guide
• What is the principle of speciality in extradition?
• UK extradition treaties: how they work and Mutual Legal Assistance

How Gherson can assist

Gherson’s Extradition Team has extensive experience advising individuals facing complex extradition proceedings, INTERPOL Red Notices and multi-jurisdictional criminal investigations. We regularly represent clients in cases involving allegations of financial crime, corruption, politically motivated prosecutions and other cross-border matters.

If you have any questions arising from this blog, please do not hesitate to contact us for advice, send us an e-mail, or, alternatively, follow us on X, Facebook, Instagram, or LinkedIn to stay-up-to-date.

This article was first published in 2021 and has been updated in June 2026.

The information in this blog is for general information purposes only and does not purport to be comprehensive or to provide legal advice. Whilst every effort is made to ensure the information and law is current as of the date of publication it should be stressed that, due to the passage of time, this does not necessarily reflect the present legal position. Gherson accepts no responsibility for loss which may arise from accessing or reliance on information contained in this blog. For formal advice on the current law please do not hesitate to contact Gherson. Legal advice is only provided pursuant to a written agreement, identified as such, and signed by the client and by or on behalf of Gherson.

©Gherson 2026