Einstein's last great problem: who owns his house?

"My paradise," was how Albert Einstein described the house near Berlin where he spent his last summers in Germany, pottering around in the garden, messing about on his boat and penning the famous "Why War?" letters to Sigmund Freud. Paradise is not yet lost, though its fabric has been weakened by the passage of time, and a row about ownership rights has landed Einstein's relatives in purgatory.

While the heirs and the village of Caputh slug it out in court, the timber frame of the listed monument, built for Einstein in 1929 by the leading Bauhaus architect, Konrad Wachsmann, is rotting away. It will not be repaired until somebody decides who the rightful owner is.

The battle, now in its sixth year, has become a test case for thousands of Jewish property claims meandering since reunification through Germany's legal labyrinth. Weighing in at opposite corners are two different arms of the state, several Jewish institutions, and an old woman living in New York.

The village bases its claim on the Nazi law of 1935, which transferred the house into state ownership, "compensating" the family with 5,000 Reichsmarks - less than a tenth of the property's real value. By then the physicist was living in California, never to return, and the house was occupied with his permission by a Jewish orphanage.

The children were allowed to stay there until Kristallnacht, 9 November 1938, when the headmaster of the local school and his pupils ransacked the place. The orphans were taken to Berlin, many of them eventually ending up in Auschwitz. Einstein's former retreat was handed over to a Nazi girls' organisation, and later became a Luftwaffe rest home.

Caputh's determination to cling on to a dwelling its own inhabitants had profaned, and turn into into a shrine dedicated to a man they had driven away, has united all other claimants in outrage. "How can these people have the chutzpah to pretend that Einstein was their favoured son?" asks Gary Smith, the head of the Einstein Forum. "How little shame they have."

Mr Smith's foundation, sponsored by the regional government, is allowed to use the house during the week for seminars, but at weekends the village opens the doors to tourists. Caputh, a community of 3,000 impoverished souls a few miles outside Potsdam, is broke, however, and cannot afford to pay for its upkeep. "I could raise money for repairs in a minute," says Mr Smith, "but I'm not allowed to."

The Einstein Forum would like to use the building as a guest house for visiting academics, but Mr Smith is at the end of an almost infinite chain. Einstein's legal heirs, according to US law, are the Jewish groups named in his will, and the family. The biggest institutional heir, the Hebrew University of Jerusalem, has indicated that it would be willing to hand over its 11.6 per cent stake to the Forum. It would be the first-ever gift from an Israeli organisation to a foundation set up by the German state. Though the other groups, including the United Jewish Appeal, have made no such pledge so far, Mr Smith hopes they would follow the university's example.

The family's stake, accounting for 50 per cent, is held by Eva Kayser, the closest descendant. Mrs Kayser, who has never seen the house, is the widowed second wife of Einstein's son-in-law, Rudolf Kayser. He was previously married to Ilse, Einstein's step-daughter from his second marriage. "What's complicated about that?" Eva Kayser asks. She lives in New York, and has no ambition to fix roofs. She only wants compensation, estimated in the region of DM1m (pounds 2.6m ).

Whether scholars can return to Einstein's house to conduct erudite discussions about life, the universe, and everything is now up to the courts. Mrs Kayser is optimistic that their deliberations will not take another six years. "We have waited for so long," she sighs. "I hope it's not going to be much longer."