The case of Julian Assange raises important questions about the European Arrest Warrant.

In theory, the rationale for the warrant is very persuasive. The advances in communication and travel that have turbocharged international business have also facilitated a growth in international crime. This is why we are seeing increased trafficking not just in drugs and arms, but in women and children for sex, and people generally for exploitative labour. There is also a quiet growth in the sale of organs, women's eggs and nuclear material.

The problem with old-style extradition pro­cesses is that, in the hands of good lawyers, they can be made to run for ever. The European Arrest Warrant was invented to expedite the transfer of people wanted to stand trial or serve a sentence within the EU and partner European countries: the underlying principle is that even though the signatory countries have different legal systems, they all provide fair trial in accordance with human rights standards.

So, it is deemed unnecessary to examine the evidence before transfer and years of delay are cut short. All a court here has to do is establish the identity of the person arrested, confirm the warrant has been properly issued and ensure that the offence for which he or she is sought constitutes a crime in the UK. If, for example, adultery was a crime in Portugal, we would not be expected to surrender a wayward spouse.

Crimes and misdemeanours

The European Arrest Warrant (EAW) entered UK law in 2004. Its midwife was the then home secretary, David Blunkett, who has since had the grace to say: "I was insufficiently sensitive to how the arrest warrant might be used for misdemeanours carrying greater sentences elsewhere than they would here."

The EAW has been used to fast-track the handover of large numbers of people wanted on extremely low-level charges in places such as Poland and Bulgaria - sometimes for simply overdrawing on a credit card without prior agreement. It is tempting to think it has become part of the effort to reduce immigrant numbers.

An arrested person can spend lengthy periods in custody abroad before any trial - Italy, for one, has a poor record for holding people for years on remand. And so what has become clear over the period of the EAW's operation is that these handovers produce too many cases where there is grave injustice. In one instance, the British courts ordered a man called Edmond Arapi to return to Italy to serve a 16-year sentence for murder - in a city he had never visited, and which took place on a day when he was at work in the UK.

Such is the managerial and technocratic approach of our courts that he was unable to produce overwhelming evidence showing he was innocent. British courts ordered Arapi's extradition, but luckily for him Italy finally withdrew its extradition demand on the last day of his appeal following a campaign by Fair Trials International. He was eventually released, but only after a period in jail away from his young family.

The Assange case also turns a spotlight on some of these issues. Sexual assault does not usually fall into the category of misdemeanour. One of the charges against Assange is rape, which sits high on most lists of egregious crimes; however, Sweden has designated this particular alleged offence as the most minor form of rape in its calibrated system. The facts of the allegations are not simple and are clouded by misread cues and profound differences in legal approach.

In Sweden, rape is the use of physical force in acts of sex. For us, the notion of consent is what matters and, in the current disclosures from the complainants, there is no suggestion that there was ever withdrawal of consent. Yet consent is not an issue in Sweden. This means that what constitutes rape in Sweden is distinctly different from here.

Also, although Assange denies the charges vehemently, he is unable to put his case before the extraditing courts, as the detail of what happened is not an issue for them.

It has also come to light that in Sweden sex cases are invariably tried behind closed doors, which contravenes our understanding of open justice. Women should be able to give evidence behind screens or by video link if they require this protection, but hearings should be open so that the public knows what is going on.

Rules of the game

Whatever the outcome, the case raises issues about how the EAW works. I have no doubt that our legal luminaries do not want a hole blown in the Eurowarrant system, as it is such a powerful tool in dealing with international organised crime. In January, a father and son, heads of a sex-trafficking ring, were sentenced in Man­chester to a total of 27 years in prison. The son had raped, battered and prostituted young women from eastern Europe. The father had supplied women and offered advice on running the business and was rightly extradited from Spain, using the fast-track method, to stand trial.

However, the EAW as currently drawn is a blunt instrument. It is based on a blind faith in the criminal justice systems of other European countries, but fundamental rights do not receive the same level of protection in all countries. My concern is that, in seeking to integrate law enforcement, we surrender safeguards that are essential to liberty and human rights.

Just imagine what it means to be arrested and sent abroad to face a system that is unfamiliar and where you do not speak the language, where you will be kept in custody because you are a foreigner, where the rules of the game may mean hearsay evidence is readily accepted and where the hearing may be in private.

The Eurowarrant system should contain far greater protections and we should be calling for a European review to ensure that basic rights to a fair trial are respected across Europe.

Helena Kennedy is a barrister and Labour peer