It has been a difficult goal, believes Mats Ljungqvist who, together with colleague Per Lindqvist, prosecuted the highly publicized case.

On the other side, they have had one of the world's leading spy organizations, the Russian intelligence service GRU, or the "elite of the elite" as Mats Ljungqvist himself describes them

- It is difficult to gather evidence in this type of case, he says.

Comprehensive confidentiality

He attributes the fact that there was a conviction after all to the good cooperation that the prosecutors had with the Security Police.

They have had to use special methods in order to prosecute the two brothers.

But exactly what that means, the public will not be able to take part.

- What kind of methods they are, I cannot go into for the simple reason that they are methods that need to be protected.

Parts of the judgment are shrouded in secrecy and the prosecutors have a certain ban on disclosure.

Therefore, the question of what was decisive in reaching a conviction also becomes difficult to answer.

- The absolutely most important evidence is secret, says Mats Ljungqvist.

Traces of encryption software

In court, however, it was established that, among other things, traces of both encryption programs and classified documents were found on the older brother's private computer.

In addition, he has handled large sums of cash which the court does not believe he was able to explain.

Per Lindqvist tells TT that he believes that the most important thing in reaching a conviction has been to demonstrate that several different circumstances are connected.

- You can see common threads, you can compare things objectively and simply and clearly and when you put it together.

In that way, it is not possible to draw any other conclusions than those that the district court has made.

Will appeal

The brothers were sentenced against their denial and have announced via lawyer Anton Strand that they will appeal the verdicts.

Mats Ljungqvist says that he feels confident about a possible continuation in the Court of Appeal.

- I particularly want to point out the work that the district court has put in, on a detailed level, to argue about the verdict that has now been announced.

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See a summary of the course of events that led to the prosecution of the brothers in the clip.

Photo: SVT