It was the first big war crimes trial based on the principle of universal jurisdiction: the Rwanda trial at the Higher Regional Court in Stuttgart.

Two Rwandan men were accused of leading a rebel group in eastern DRC for years, while they were living a normal life in Germany. In 2015, Ignace Murwanashyaka, the main accused, and his deputy Straton Musoni were sentenced to 13 and eight years respectively for aiding and abetting war crimes.

The principle of universal jurisdiction makes proceedings like this possible. It says that serious crimes can be punished in a country other than the one where they were committed. This applies above all to crimes prohibited under international law, such as war crimes.

On Thursday the Federal Court of Justice in Karlsruhe will announce whether the verdict will stand. The Federal Prosecutor's Office is calling for Ignace Murwanashyaka, as the long-time president of the FDLR (Democratic Forces for the Liberation of Rwanda), to be sentenced as a perpetrator of the crimes, not just for aiding and abetting them. The defense is calling for the suspension of proceedings or a retrial. A revision of the verdict could have far-reaching consequences, including for future criminal proceedings.

Read more: Can German courts prosecute Rwandan war crimes?

Too little information for the victims?

For Andreas Schüller of the human rights organization European Center for Constitutional and Human Rights (ECCHR), the Rwanda trial had an "ambivalent" outcome.

The procedure proved that it was indeed possible to hold war crimes trials of this magnitude in Germany, the lawyer said in an interview with DW. However, one huge omission was "that such a mammoth trial is being conducted here, but the Federal Republic has not ensured that people in the region itself were not given adequate information about the trial.” This meant that the potential effect of the trial on those concerned, and on their sense of justice, was squandered.

Sylvain Lumu, the managing director of Ligue des électeurs, a human rights organization from the Democratic Republic of Congo, wants people to see the proceedings as an important part of coming to terms with the past. "Anything that helps process the crimes also helps the victims," he said.

He understands the criticism of the fact that the trial didn't take place closer to the victims, where the crimes were committed, but he believes there are other priorities. "I don't think trials of this dimension would be possible in Congo or Rwanda," Lumu told DW.

For this reason, Andreas Schüller of ECCHR sees the principle of universal jurisdiction as a chance to "secure evidence that may no longer be available in a few years' time."

Read more: 'We can grow from trauma,' says Rwandan genocide survivor helping refugees heal

The goal: Trials in the perpetrator states

The Green Party's foreign affairs expert Omid Nouripour warns against resting on our laurels following the initial successes based on the principle of international law. "We can't stop striving for justice in Rwanda now that we can actually bring a case in Norway as well," Nouripour told DW. "It would certainly be far better if, instead of war criminals from the Central African Republic being put on trial in Germany, they were put on trial in the Central African Republic.”

International law expert Andreas Schüller points to initial positive developments in this regard. In 2017, the Higher Regional Court in Hamm referred a war crimes trial back to Rwanda because it anticipated that the accused would be tried there under the rule of law. Back when Murwanashyaka and Musoni were put on trial, the situation was different.

Will there be more mammoth trials?

Eike Fesefeldt of the public prosecutor's office in Stuttgart recently wrote a guest article for the magazine Legal Tribune Online, in which she said that the German judiciary should prepare itself for even larger criminal proceedings – against high-ranking war criminals from the Syrian civil war, for example.

This is precisely what Andreas Schüller and his colleagues are working on. The ECCHR has stated that it has brought several charges in German courts against alleged war criminals in Syria, including people close to the Syrian ruler Bashar al-Assad. An arrest warrant has been issued for Jamil Hassan, the head of the Syrian Air Force Intelligence Directorate. "We want to see proceedings being initiated against state actors as well. because in the Syrian conflict in particular, it is, of course, the Assad regime that bears the greatest responsibility for crimes under international law," explains Schüller.

Since 2012, the Federal Prosecutor's Office has been conducting systematic surveys of Syrian refugees. Many among them are victims, but there are also suspected perpetrators of war crimes. "The German authorities have direct access to incriminating material," Professor Robert Heinsch of the Institute for International Humanitarian Law at the Ruhr University in Bochum said in an interview with DW.

Read more: The dark secrets of Germany's forgotten colonial past

Verdict will have a big impact

However, Heinsch warns against excessive euphoria, especially with regard to possible lawsuits against political leaders: "A German court cannot easily accuse the foreign minister or the head of state of another country as long as that person is in office," he said.

At international tribunals, such as the International Criminal Court in the Hague, a head of state could be stripped of his or her immunity by a UN Security Council resolution, he continued. This was not an option at a Higher Regional Court.

So when the German Federal High Court passes judgment on 20 December, there's far more at stake than just the fate of the two alleged Rwandan war criminals. If the Stuttgart verdict is confirmed, it will open the door wide for further trials. But if the court overturns the verdict, the trials of war criminals in Germany could in future be even longer, even more expensive, and even more difficult.