Germany’s Federal Supreme Court has given its approval for a Munich court to try accused Nazi war criminal John (Ivan) Demjanjuk.

Following last week’s decision, the 88-year-old man, who has spent most of the post-war period as a US citizen, may now be extradited to Germany, despite the protests of family members who claim he is too frail.

Meanwhile, German prosecutors are trying to build their case against him, going through Nazi-era files in German archives. Demjanjuk, who was born in Ukraine, is accused of participating in the murder of 29,000 European Jews at the Sobibor extermination camp in Poland, where he was, allegedly, a supervisor for seven months in 1943.

Germany may apply for his extradition because 1,900 of his alleged victims were German Jews, and because he stayed in a Munich displaced persons camp after the war, according to reports.

Charlotte Knobloch, head of the Central Council of Jews in Germany, told a Munich newspaper she hoped the court would “do everything legally possible to speed up the process so that Demjanjuk can be held accountable during his lifetime”.

Demjanuk came to the USA after the Second World War and became a citizen in 1958, changing his first name to John. He stood trial in 1986 in Israel, where he was convicted of having been “Ivan the Terrible”, a guard at Treblinka. He was condemned to death but he was later released when Israel’s high court was unable to confirm his identity.

In 2002, a US District judge found that he had worked at more than one Nazi death camp. He has been stripped of his US citizenship because he obtained it under false pretences, lying about his Nazi past. In May, he lost his final appeal to avoid deportation.

Demjanjuk himself has insisted that he served in the Soviet army and was captured by Germany in 1942. His son, John Demjanjuk, recently told Associated Press that his father could not handle another trial.