Recent high-profile extradition cases have breathed new life into the old question of whether extradition relations between the US and the UK are imbalanced. On 12 February 2020, the Leader of the Opposition stated in Parliament “this lopsided treaty means the US can request extradition in circumstances that Britain cannot”. The Prime Minister replied: “to be frank, I think the right honourable Gentleman has a point in his characterisation of our extradition arrangements with the United States”[1]. It is a question that has arisen time and again since the UK ratified the US/UK Extradition Treaty 2003 (‘the 2003 Treaty’). So, where does the truth of the matter lie?

The case for imbalance 

The early cases under the 2003 Treaty proved to be controversial, with cases such as the “Natwest Three”; Ian Norris; and Babar Ahmed receiving extensive media coverage. From the beginning, a consistent theme in the coverage was that the 2003 Treaty was imbalanced in favour of the US. Those arguments have focused on three issues: (a) the requirement to prove an evidential case; (b) the existence of a discretion whereby the US Secretary of State can refuse extradition; and (c) US extradition requests based on conduct that largely, or wholly, took place in the UK.

The evidential threshold

The most common objection to the 2003 Treaty is that the UK is required to meet a higher evidential threshold than the US before extradition will be ordered. There are two limbs to this objection.

First, Article 8(3)(c) of the 2003 Treaty provides that UK extradition requests must be supported by “such information as would provide a reasonable basis to believe that the person sought committed the offense for which extradition is requested”, better known as the “probable cause” test. By contrast, section 71 of the Extradition Act 2003 (‘the 2003 Act’) provides that an arrest warrant in an extradition case may be issued “provided there are reasonable grounds for believing that … there is evidence … that would justify the issue of a warrant for the arrest of a person accused of the offence within the judge’s jurisdiction”. This is commonly referred to as the “reasonable suspicion test”.

Second, §3184 of Title 18 of the US Code requires a US extradition judge to determine whether the extradition request contains “evidence sufficient to sustain the charge under the provisions of the proper treaty or convention” which, in the case of UK extradition requests, is evidence of probable cause. There is no equivalent process under the 2003 Act in relation to US extradition requests.

Frequent claims in the media, and in Parliament, that the difference in these tests favoured the US caused the then Home Secretary, Theresa May, to request that the alleged imbalance under the 2003 Treaty be considered in the review of the United Kingdom’s extradition arrangements conducted by the Rt Hon Sir Scott Baker (‘the Scott Baker Review’) which reported in 2011. The Scott Baker Review concluded that: (a) both tests are based on reasonableness; (b) both tests are supported by the same documentation; and (c) both tests represent the standard of proof that police officers in the US and the UK must satisfy domestically before a judge in order to arrest a suspect.

In 2014, the House of Lords Select Committee on Extradition Law (‘the Extradition Select Committee’) returned to this issue and heard evidence from a former US federal prosecutor to the effect that the two tests are “functionally the same”, and that he could not think of a single case that “would have turned on the difference between those two standards”. The Extradition Select Committee concluded that, although the tests are different, “whether this difference has any practical effect is debatable. The view that experience to date demonstrates that they are ‘functionally’ the same is persuasive”.

Two further points are worth noting under this heading.

First, many US extradition requests, including all federal felony prosecutions, are issued on the basis of a grand jury indictment. This means that the allegations in the extradition request have been tested before a grand jury in the US who have reviewed the evidence and decided that there is sufficient evidence to charge the defendant with a crime (see Norris v USA [2009] EWHC 995 (Admin) at §33). While there may be grounds to criticise this process – grand jury proceedings are held in secret and the defendant has no right to be present – it is a process by which the evidence supporting the charges is scrutinised before the request is issued, and it is not a process that UK prosecutors have to go through[2].

Second, there is no evidence that the US refuses high numbers of UK extradition requests on the basis of the allegedly higher evidential threshold that UK prosecutors are required to meet. Indeed, the Extradition Select Committee received evidence from the Home Office that between 1 January 2004 and 31 January 2014, 14 US extradition requests had been refused by the UK and, during this period, the US did not refuse a single UK extradition request. On 23 January 2020, the Minister for Crime, Policing and the Fire Service confirmed that this remained the position[3].

Discretion v obligation to extradite

The criticism that the US Secretary of State retains a discretion to refuse extradition, whereas the UK Secretary of State does not, was most recently voiced by David Davis MP in Parliament on 23 January 2020[4].  This criticism is not based on the wording of the 2003 Treaty, which imposes an equal obligation on both parties to extradite, subject to the provisions of the Treaty (Article 1). Rather, this objection is based on the wording of the domestic legislation governing the decision by the Secretary of State in each jurisdiction to order extradition.

In both jurisdictions, a court is required to make an initial determination as to whether the individual is extraditable (Extradition Act 2003 ss. 75-92; Title 18, §3184), and the case is then sent to the Secretary of State for a decision as to whether to order extradition. In the UK, section 93 of the 2003 Act provides that the Secretary of State must first consider whether she is prohibited from ordering extradition by virtue of sections 94 to 96 and, if she is not, then she must order extradition (subject to a number of narrow exceptions). In the US, §3186 of Title 18 provides that the Secretary of State “may” order extradition.

The only case cited in support of the US exercising its discretion against extradition, is the recent refusal to surrender Anne Sacoolas to face charges of death by dangerous driving. This is, in fact, the only case in which the US has refused a UK extradition request. It is not, however, a case in which the US Secretary of State has exercised his discretion pursuant to §3186 of Title 18. Rather, it would appear to be a case in which the US Department of State has refused to send the extradition request to a judge for a decision under §3184 because Anne Sacoolas has made a claim to diplomatic immunity.

While there may be arguments as to whether Ms Sacoolas’ claim to diplomatic immunity is appropriate, what is clear is that this is not a case where the terms of the 2003 Treaty have caused extradition to be refused in circumstances that would not apply to the UK. The 2003 Treaty is silent with respect to diplomatic immunity, which is an independent principle of international law. The UK courts have confirmed that, in an appropriate case, diplomatic immunity would form proper grounds to refuse an extradition request pursuant to the Diplomatic Privileges Act 1964 (Bat v Germany[2011] EWHC 2029 (Admin)). It follows that the Sacoolas case does not support the proposition that the 2003 Treaty is one-sided.


One of the most frequent criticisms in relation to the US/UK extradition arrangements was summarised in 2012 by the Home Affairs Select Committee in the following terms: “[the US] has the power to reach out around the world and – provided there is a very, very tenuous connection with the US – generally has the power to prosecute”. This issue has been considered on a number of occasions, in particular in the case of the ‘NatWest Three’, where the Divisional Court held that the 2003 Act did not provide a discretion to refuse extradition on grounds that the appropriate venue for trial was the UK, unless a human rights ground was engaged. Partly as a result of this case, on 14 October 2013 the UK introduced a ‘forum’ bar in section 83A of the 2003 Act, allowing extradition to be refused where: (a) a substantial measure of the requested person’s relevant activity was performed in the UK, and (b) extradition would be contrary to the interests of justice. The proposed introduction of this bar prompted the US Embassy to state in a Factsheet in 2011 that “the introduction of the “forum provision” [into the 2003 Act] is neither necessary nor justified”.

The need for further safeguards

On 23 January 2020, David Davis MP made the case in Parliament for the reform of the 2003 Treaty[5]. Citing the cases of the NatWest Three; Ian Norris; Christopher Tappin; and Gary McKinnon, as well Dr Mike Lynch who may be facing extradition to the US, he argued that “the American judicial system operated to favour American business” and that “the United States is going after white-collar businessmen and seeking to be the judge, jury and executioner for global commercial deals”. Citing the alleged imbalance under US domestic law that favoured the prosecution over the defence, he argued that the 2003 Treaty ought to be amended so that extradition can be challenged in the UK on the basis that the request does not disclose a probable cause, and to give the Secretary of State a discretion to refuse extradition. On analysis neither of these amendments are necessary.

First, as noted, both the Scott Baker Review and the Extradition Select Committee concluded that there was little difference in practice between the requirement that a US extradition request show “reasonable suspicion” and a requirement that a UK request demonstrate “probable cause”. Further, even if the 2003 Act included a provision that enabled requested persons to challenge an extradition request on the basis that it disclosed no probable cause, it would not have assisted any of the individuals cited by Mr Davis. In the NatWest Three case, the Divisional Court found that, while the prosecutor did not have to demonstrate as much, “a prima facie case is shown on the documents accompanying the request” (R (Bermingham and Ors) v SFO and Anor [2007] QB 727 at 773). Similarly, the Divisional Court concluded in the Gary McKinnon case that “on any basis, there is a prima facie case against Mr McKinnon” (McKinnon v United States [2007] EWHC 762 (Admin) at paragraph 39). In the event, extradition was refused in the case of Mr McKinnon, but the NatWest Three and Christopher Tappin pleaded guilty following extradition, and Ian Norris was convicted by a federal jury of some of the counts in respect of which he was extradited. In none of these cases is there any evidence that an ability to challenge the evidential threshold in the extradition proceedings would have precluded extradition.

Second, as the decision of the Secretary of State in the Gary McKinnon case shows, the UK does have a discretion to refuse extradition in human rights cases. In addition, the forum bar in section 83A allows extradition to be refused in some cases where a substantial amount of the conduct alleged in the extradition request occurred in the United Kingdom. It was on this basis that the US extradition request in relation to Lowri Love was refused (Love v United States [2018] 1 WLR 2889). Further, insofar as there is evidence in any given case of an abuse of process by a US prosecutor, it is well established that US courts have power to refuse extradition in those circumstances (R (United States) v Bow Street Magistrates’ Court [2007] 1 WLR 1157).

The only remaining justification for additional safeguards under the 2003 Treaty is the suggestion by Mr Davis that there ought to be greater protection against extradition to the United States because US prosecutions are unfair. This is, in fact, potentially a much wider argument: if alleged unfairness by domestic prosecutors should justify additional safeguards in relation to the US, then why should there not also be additional safeguards in the UK’s extradition relations with other states in respect of which there is no requirement to establish an evidential case? Further, if an ability to challenge the probable cause/reasonable doubt requirement would not in fact have assisted any of the allegedly unfair US requests cited by Mr Davis, then it is difficult to conceive of another safeguard that would meet the point short of a requirement to prove a prima facie case. This step was considered in detail in the Scott Baker Review, but rejected on the basis that extradition judges were able to subject cases in which there was no prima facie case requirement to sufficient scrutiny to ensure that any abusive request was identified and dealt with appropriately.

An imbalance that favours the UK?

Finally, it is worth noting that the 2003 Treaty has direct effect in US domestic law. Thus, a judge at an extradition hearing is required by Title 18 §3184 to determine whether the requested person is extraditable by reference to the provisions of the 2003 Treaty. By contrast, the 2003 Treaty gives rise to no personal rights enforceable by individual citizens under UK law (R (Norris) v Home Secretary [2006] 3 All ER 1011) and liability to extradition is determined by reference to the statutory criteria under the 2003 Act. That Act contains a number of mandatory grounds of refusal that do not appear in the 2003 Treaty, in particular: (a) passage of time; (b) forum; and (c) the requested person’s mental and physical health. While these may be issues that could cause the US Secretary of State to exercise his discretion to refuse extradition under §3186, unlike the position under the 2003 Act, US law does not require extradition to be refused when the criteria for each of these grounds of refusal is established. To that extent it may be said that the extradition relationship allows the UK authorities greater scope to refuse an extradition request; an assertion that is supported by the figures put before the Extradition Select Committee.


Since its inception there have been claims that the US/UK Extradition Treaty is imbalanced. On analysis, the only difference in the legal tests applicable under the Treaty is the evidential threshold which both the Scott Baker Review and the Extradition Select Committee concluded was, in practical terms, the same as the test applicable to UK extradition requests. While it is correct that UK extradition requests may be challenged in US courts on the basis that the evidential threshold is not met, there is no evidence that this has resulted in UK extradition requests being refused, or that a similar requirement under UK law would have altered the outcome in any US extradition cases. Similarly, while not a treaty issue, there is no basis to the objection that US law permits the Secretary of State a discretion with respect to extradition in circumstances where this discretion has never been exercised to refuse a UK request.

The other objections to the US/UK extradition relationship are not related to the Treaty but rather are broader objections to the exercise of jurisdiction by US prosecutors. Any lack of reciprocity in this respect does not derive from the Treaty but rather from the restraint of UK prosecutors: there is nothing in the 2003 Treaty to prevent the UK, if it so chose, to adopt the same approach to jurisdiction. In this context, the allegation of Treaty imbalance serves as a proxy for general criticism of US criminal justice policy. As such, despite the fact that the allegation is unfounded, it is unlikely to disappear any time soon.

[1] Hansard, 12 February 2020, CM Vol 671, col 845.

[2] The Grand Jury procedure was abolished in the UK pursuant to the Administration of Justice (Miscellaneous Provisions) Act 1933.

[3] Hansard, 23 January 2020, Cm, Vol 670, Col 508.

[4] Hansard, 23 January 2020, Cm, Vol 670, Col 506.

[5] Hansard, 23 January 2020, Cm, Vol 670, Cols 504-508.

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