The accused -- a Vietnamese-Czech man identified only as 47-year-old Long NH -- allegedly rented and drove the van used in last year's abduction of a fugitive Vietnamese state company official in a central Berlin park.
The kidnapped man, Trinh Xuan Thanh, 52, who was seeking asylum in Germany, was quickly spirited back to Hanoi, where he was sentenced this year to two life terms in prison on corruption charges.
Germany condemned the July 23, 2017, operation as a "scandalous violation" of its sovereignty and a "gross violation of international law".
It expelled two Vietnamese diplomats, summoned the ambassador several times and put on ice a strategic bilateral partnership.
Communist-ruled Vietnam has insisted that Thanh, the former head of PetroVietnam Construction, returned voluntarily to face embezzlement charges.
Vietnam, like China, has recently convicted scores of figures from its business and political elite as part of an anti-graft drive which observers say also serves to settle scores between hardline and reformist factions.
German prosecutors are investigating a high-ranking Vietnamese security official, General Duong Minh Hung, who allegedly commanded the abduction in Berlin before returning to Vietnam, the Sueddeutsche Zeitung daily reported last month.
Hung is suspected of holding more than 100 cellphone talks or text message exchanges with the agents from his temporary "command centre" inside a hotel, a few blocks from the Tiergarten park where the abduction took place.
Long NH, the van's alleged driver who was arrested in the Czech Republic on August 12 and extradited to Germany on August 23, is the only suspect in German custody.
Once among thousands of so-called guest workers in communist East Germany, he was later denied asylum and resettled in Prague, where he most recently ran a currency exchange business.
Thanh and his female companion were first taken to the Vietnamese embassy in Berlin before she was flown to Hanoi, while Thanh was abducted to Vietnam "by unknown means", prosecutors charge.
Long NH, who had also allegedly rented a BMW X5 sedan that had been used for surveillance, is charged with working for a foreign intelligence service and aiding in an abduction, which each carry up to 10 years in prison.
News weekly Der Spiegel has reported that German investigators reconstructed the abduction using the van's GPS system, witness statements, footage from multiple security cameras on streets, petrol stations and inside hotels, and Thanh's smartphone, which was left at the scene.
It said that the Vietnamese snatch team found Thanh -- who had been living in seclusion in Berlin with his wife and children since mid-2016 -- when his secret lover, Thi Minh P.D., flew in from Paris to meet him at a hotel and the two then took a walk in the Tiergarten park.
The report said that in the violent struggle Thanh hit back at his attackers and the woman lashed out so strongly that "eyewitnesses thought she had suffered an epileptic seizure".
The Sueddeutsche previously reported that in the abduction, "it seems that half the embassy was involved" -- with the mission used as a drop-off stop in the kidnapping, some people involved being accredited diplomatic staff, and the wife of the defence attache booking the flights home for the agents.
The article also said that investigators had found blood traces in the rented van, pointing to a struggle.
The Berlin court has scheduled 21 days of hearings until May 17.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
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