A German court has convicted a Syrian refugee of being an accessory to a war crime against humanitarian operations over his participation in the 2013 kidnapping of a Canadian United Nations observer.

The Stuttgart state court Wednesday sentenced the defendant, who has been identified only as Suliman Al-S. in line with German privacy rules, to 3½ years in prison.

Prosecutors haven't identified the observer but the facts released correspond with those of the kidnapping of Canadian lawyer Carl Campeau, who was abducted from a Damascus suburb. He escaped after eight months.

Campeau confirmed to CBC News in an email statement that he was the observer at the centre of the case.

"How do I feel about the verdict? I feel satisfied," Campeau said.

The court found the defendant backed the kidnapping and offered to serve as a guard, but didn't find conclusive proof that the Nusra Front, al-Qaeda's branch in Syria, was behind the kidnapping or that the defendant belonged to it.

Campeau said the accused's role was "minor." He was a guard for only a couple of weeks, and his role was limited to bringing food and allowing Campeau to use the toilet.

Campeau added that he believed the punishment "must be proportional to the crime," which is why his lawyer asked the court to deliver a lighter sentence but still find him guilty.

"I found that a guilty verdict was appropriate, but I did not wish for him a sentence that would keep him much longer in jail. I was concerned that the accused could become even more radicalized because of a severe sentence.

"The trial has been difficult for me," added Campeau. "I testified for almost nine days in total. At times, I felt like being the accused."

He said the defence did what they could to discredit him as a witness.