A few summers ago a Scottish teenager stole a lilo from a beach stall in Turkey.

She'd had a few drinks and was on her way home. "It wasn't the crime of the century," concedes Malcolm McBain. "For some reason she thought it was hilarious. When she sobered up, she felt bad and took it back. Foolishly, she thought that would be the end of the matter...."

It wasn't. Turkish authorities were determined to prosecute. The result? A legal headache for the girl and paperwork for McBain, a Scottish prosecutor. His desk is where Scotland's sometimes eccentric legal system meets the rest of the world. As the planet shrinks, it is a busy place. And not just with drunken holiday larks.

After he put down the Lilo thief file, McBain picked up another. "The next request I received related to a political assassin believed to be living in Scotland," he explains matter-of-factly over coffee in a room above Edinburgh Sheriff Court.

McBain, 40, won't - can't - say more about the alleged assassin. Nor should he. "The requesting country wanted a statement taken from him," he says, weighing every word. "That is the variety of the stuff we can receive."

McBain's job isn't secret. But it may as well be. Because so few people know what it is that he does. And because so much of his work is politically or legally sensitive.

There is even confusion within the prosecution service about McBain's role. His official title is head of mutual legal assistance at the Crown Office's International Co-operation Unit or ICU.

His actual job? To make sure evidence for investigations here and abroad can cross borders quite as easily as criminals do.

Along with colleague David Dickson, the advocate depute responsible for extraditions, McBain has never been busier. Business at the ICU, the single hub that keeps Scottish law enforcement plugged in to the rest of the world, is booming as crime globalises. But the unit's work also raises all sorts of questions about the very nature of Scots Law and those of the other legal cultures it interacts with.

How much crime crosses borders? What exactly constitutes a crime? Why is something a prosecutable offence in one country and not in another? How do foreign countries obtain evidence in Scotland that will stand up in their courts - with very different legal niceties. And, above all, how does Scotland - a stateless legal jurisdiction - get on with other countries?

The Crown Office - which often prefers to work in the shade rather than the light - has opened up the ICU for the first time to The Herald. It has done so because of the sheer scale of often unrecognised work being carried out by the unit.

So how many cases are they handling? How much cross-border crime is being investigated or detected? Well, from April through November of last year, McBain's team executed 214 requests for legal assistance from overseas.

That is more than one every working day. It also saw 127 of its own requests carried out by foreign colleagues.

Requests range from anything to taking witness statements on oath before a judge - or even taking over an entire case - to providing phone records. Cases under investigation range from, yes, lilo thefts to assassinations.

But the ICU doesn't merely import and export evidence. It does the same with people. Its extradition conveyor belt - through Edinburgh Sheriff Court - has never been busier.

There were 141 requests for extraditions in the 2013-14 financial year and another 101 in April-November 2014, leading to 94 and 68 arrests.

Some, of course, contest their extradition. Nine new such appeals against extradition were launched in April-November, generating hundreds of hours of highly expensive court time. But detailed figures, seen by The Herald Magazine, show that most go without a fight. Seventy people surrendered to incoming requests for extradition.

Those sent overseas to face trial included alleged human trafficker Ion Cirpaci, sent to his native Romania last May. Or Jan Eichmann, wanted for murder in Poland, who was returned in January 2014.

Scotland also sought 27 individuals overseas in the full year 2013-14 and another 22 in the first eight months of 2014-15. There were 12 returns in 2013-14 and nine in April-November 2014.

Several high-profile returnees are close to going to trial and cannot, for legal reasons, be named. But wanted men delivered to Scottish justice and convicted in recent years include serious sex offenders.

Donald Steele, who was removed from Thailand, was jailed for six years for attempted rape and lewd and libidinous practices in 2012. George States got two years nine months for sex offences in 2013 after being extradited from Bulgaria.

The number of such cases is set to rise, at least within the EU as the UK signed up to part of the Schengen borders deal. Starting last month, the details of some 40,000 wanted criminals and missing persons from most of the EU will be on to the UK's Police National Computer or PNC.

The courts expect to be so busy that the number of sheriffs trained to handled such cases has jumped 50 per cent. Dickson is also bracing himself. "We are already moving towards 100 extraditions a year," he says. "The number of cases we have going through the courts now is the biggest we have ever had.

"There are something like 50 live cases and seven appeals.

"That may not sound a huge number in relation to the whole prosecution work, but it is a big increase and it can only rise with Schengen."

This is good news. That, at least, is the consensus in Scottish law enforcement. London tabloids - and even prominent Conservative politicians - haven't always agreed.

Most of extraditions, in and out, are made under European Arrest Warrants (EAW).

Yet just a year or so ago, Tory Eurosceptics were suggesting abolishing EAWs amid tabloid headlines about British subjects being packed off to dubious regimes and UK police spending valuable time chasing Polish chicken thieves.

After an outcry from senior officers, including those in Scotland, Home Secretary Theresa May backtracked and kept EAWs. Later came Schengen. Progress, Scottish detectives gave a sigh of relief.

Now the coming referendum on EU membership puts this - and potentially - wider cross-EU justice co-operation at risk.

Some in law enforcement aren't happy with that. "The criminals aren't going to stop working together," said one insider. "Neither should we."

But an increasingly co-operative EU-wide crime-fighting regime doesn't mean everyone agrees on what constitutes a crime. And that poses issues of its own.

Before prosecutors in Scotland and another country, inside the EU or out, co-operate they have to establish something called "dual criminality".

In short, that means that whatever the crime is, it must be against the law in both states.

That is easy for homicide. But it is not always straightforward.

Take Holocaust denial. This is illegal in Germany but - provided it does not involve incitement to violence - lawful in Scotland.

Another example is child-maintenance dodging. Some countries, including Poland, see failure by fathers to support children as a crime. So they may ask the Scottish authorities to help look in to the bank accounts of expat Poles here. That can't happen because the ICU can't seek court orders for things that are not criminal in Scotland, where child support is a civil court matter.

But even where jurisdictions agree something is a crime, they don't always agree that it is a crime worth prosecuting. Poland used to seek information or extradition for what right-wing papers thought were minor offences. In one notorious incident, a man was held in Wandsworth Prison for two months on an EAW for stealing a wheelbarrow.

EAWs, however, should only count for crimes that would come with a sentence of at least a year. So the Poles are learning, as one insider put it, "not to sweat the small stuff, even if what might seem like a small crime to us, may not be a small crime to them."

McBain, still thinking of his lilo thief, who was eventually served with a fine, believes Turks are coming to the same conclusion.

"Turkish prosecutors often appear to have very low level of discretion," he says.

Now a strong relationship with Turkey's legal attaché in London means receiving very minor requests is less of an issue, McBain says.

It's hard enough figuring out what a crime is, or whether it is a big enough crime to prosecute internationally. Sometimes you have to decide who prosecutes. That isn't just because many, many crimes take place online or begin in one country and end in another, such as a drug deal or complex financial fraud.

It is also because some jurisdictions base prosecutions on geography and others on nationality.

So the UK and Scotland, for example, rarely takes anybody to court for crimes committed abroad (with the exception of serious sex offences, think of Gary Glitter answering in an English court for raping teenagers in Vietnam).

But a German court can hear any crime committed by a German or against a German. "If a German is assaulted in Princes Street, a German court can assert jurisdiction," explains McBain.

Some foreign police don't bother dealing with Scottish husbands who beat their wives on holiday (a not uncommon issue). A German-style approach would mean such offences could be dealt with at home.

Germany, like many European jurisdictions, has an inquisitorial rather than adversarial system. This means witnesses are questioned by a neutral magistrate or judge rather than counsel for defence and prosecution. McBain sees some merit to this. "Sometimes it is better in a foreign country for victims," he says. The prosecutor is thinking of women who are raped on holiday, including a recent spate in Turkey. They can tell their stories to a sheriff here in Scotland who will question them, on oath, in line with foreign law. Rape campaigners believe this can lead to better outcomes than Scotland's system.

"The prosecutors overseas will have a list of questions they want asked. "If the defence has a list of questions they want asked, they may be included."

One recent example shows how this system reduces the trauma of a rape victim.

"There was a Turkish sex offence case where a minor was sexually assaulted and she gave her evidence on oath here.

"The person ended up getting six years and she gave her evidence on oath here. She did not have to go back to Turkey."

The inquisitorial system might be good for victims. But it has confused accused persons. McBain explains: "We get a lot of requests for accused people to be questioned under oath or provide a statement in a Scottish court.

"In a Scottish case, police haul the suspect in and interview them, and the suspect will say "no comment" to everything; they, after all, have the right to silence.

"Now while everyone has the right to silence, the consequences are different on the continent.

"Say someone in Scotland is accused committing a theft in Germany.

"Well, one of the worst things they can actually do is take advice from a Scottish solicitor.

"That is because most of the jurisdictions on the continent effectively have an 'opt-in, opt-out' system for accused people. Because it is an inquisitorial system you are asked to provide your evidence; if you do so the jurisdiction is under a duty to investigate everything you say

"If you choose not to provide any evidence you may have lost your opportunity to establish your defence.

"You may then be tried in your absence and the next you hear about it is that there is an arrest warrant out for you."

So a British citizen in the UK can be quizzed by a Scottish judge or Scottish police under the law of, say, Germany or Portugal or Turkey. Some countries, such as Russia, have refused to allow their citizens to be treated this way. But all that does is give such states a reputation for not being committed to fighting crime. Some British Eurosceptics have taken a similar stance, although more in rhetoric than reality.

Scotland takes a different view. Its dedicated ICU means it is seen as being easy to deal with.

"We have size on our side," says McBain. "We are a small country and all the incoming and outgoing requests have been through my hands.

"So we can tie things up quickly."

The Scottish attitude of cooperation, and the one-stop shop of a single police service, has won friends overseas.

One is �mer Faruk Altınta�, a Turkish judge who acts as liaison with the UK. He describes co-operation with the ICU as "distinctive".

He added: "I firmly believe that the more international cooperation we develop the more secure and free world we leave for future generations."

David Wilson agrees. The Detective Inspector leads Police Scotland's FAST - Fugitive Active Search Team.

"The police are the same in every country: nobody likes to see a bad guy get away," he says from the national force's crime campus at Gartcosh. "If you are expecting somebody to do something for you, then you have to step up when you have a fugitive in your country."

Baby death tragedy

HE was found in a holdall, behind a roll of old carpet in a communal hallway, with a Tesco bag over his head. Paulius Dzingus had died within hours of his birth, in Fraserburgh, in April, 2010. His mother, a newly-arrived migrant called Ineta Dzinguviene, had put clingfilm over his face.

Just a year earlier Dzinguviene had smothered another child, Paulina, in her home town of Marijampole, Lithuania. This time she had used a polythene bag and dumped her baby's remains in a suitcase. That crime may never have been discovered if it hadn't been for increasingly successful links between police and law enforcement in Scotland and the rest of the European Union.

The 29-year-old is now serving 15 years for each murder, after being tried first in Scotland, in 2011, and then, in 2014, in her native Lithuania.

This didn't happened by accident. It was the result of a textbook international co-operation between law enforcement and prosecution in two European Union member states.

Advocate Depute David Dickson, of the Crown Office's International Co-operation Uni, was at the heart of talks, brokered through Eurojust, the EU justice co-operation organised in The Hague.

"It started with a letter of request we issued for some background about Dzinguviene," he said. "A (Lithuanian) police officer went along to the family house, knowing that the body of a child had been found in Fraserburgh. He came across the body of a baby in the same circumstances in the suitcase with cellophane over its face.

"That then led to a murder investigation in Lithuania, only because we had made this request for background.

"That meant a question over jurisdiction. Lithuania can prosecute crimes that have

taken place abroad. We can't. There was

the potential the Lithuanians could seek to assert jurisdiction over our case - over the woman we had in custody for killing a baby

in Fraserburgh.

"They could, in theory, have tried her for both murders. We could only prosecute for one, not the one in Lithuania, which would have to be done over there."

How did they figure out what to do? They went to The Hague. Police and prosecutors, their trips and translators funded by EU, quickly resolved the issue at Eurojust.

Dickson explained: "In terms of the public interest, it was agreed that we would deal with our case first, because it was closer to indictment."

But the two sides also agreed to co-operate on a draft European Arrest Warrant - the document that has done more than any other measure to ensure EU nationals cannot seek refuge from justice in another member state.

So the Eurojust deal meant that, whatever the verdict, there would be a sting in the tail for Dzinguviene when she went for trial for the murder of her baby at the High Court in Livingston.

"If she was convicted, we would arrest her for extradition to Lithuania," Dickson said. "And if she was not convicted we would arrest her, too."

In fact, she was convicted. As a life prisoner, she could only be transferred out of the country to stand trial with the permission of the Justice Secretary. That permission, also arranged through Eurojust, was granted, provided she stayed in custody and was returned to serve out her Scottish sentence after trial. Which she did.

The Dzinguviene case was relatively straightforward. She committed two crimes, one in Scotland and the other in Lithuania.

But there are plenty of crimes that are truly cross-jurisdictional. And that, Dickson's colleague Malcolm McBain, reckons is when Eurojust becomes "fantastic".

The prosecutor, whose job is to get evidence rather than people across borders, is a regular visitor to The Hague. He explained why: "Let's say we have a drugs routes through Spain, France, Belgium, Holland, England and Scotland.

"There is no point in there being separate investigations. It's one crime, a transit crime.

So who prosecutes that? Spain, where the

drugs come in? Or Holland, where they were transited? Or Scotland, where the end user

was? All are valid. There is not one that is