Because Scotland has a separate legal system from the rest of Britain, a separate war crimes unit attached to Strathclyde police was set up after the passage of the War Crimes Act in 1991, in effect with the sole purpose of building a case against the retired mining engineer, now 77. Of the dozens of suspected war criminals investigated under the Act for murder or manslaughter during the Second World War, no other has been in Scotland.
Today, the Crown Office in Edinburgh will say, without naming Mr Gecas, that the investigation has been suspended. The news will be a blow to Nazi hunters around the world, who believed the case against Mr Gecas was one of the strongest of the dwindling band of suspects. A separate war crimes unit in England will continue, but has failed so far to bring a case to trial.
Effraim Zuroff, director of the Los Angeles-based Simon Wiesenthal Institute, which presented a list of suspects in Britain to the Home Office in 1986, said last night he was devastated at the news about Mr Gecas. He said he would be sending a transcript of evidence from another officer of the same Lithuanian battalion as Mr Gecas to the authorities, in the hope it might persuade them to re-open the case.
The unit of researchers and officers from Lothian police have spent an estimated pounds 600,000 travelling the world, collecting evidence from victims and fellow officers.
As a young man, Mr Gecas joined a Lithuanian police battalion as a lieutenant in charge of a platoon. The battalion killed thousands of Lithuanian Jews rounded up from city ghettos, towns and villages. By autumn 1941, when few Jews were left in Lithuania, the battalion and others were taken by the Germans to do a similar job in German-occupied Byelorussia (now Belarus).
By 1944, the battalion was being used to help prevent the Allied advance through Italy, and, in September, Mr Gecas's company was captured by the US army. He changed sides and fought for a Polish regiment, and after the war was able to launder his past and come to Britain as a Pole. By 1956, he was a British citizen. He married a 19- year-old nurse in 1959, when he was 43 and worked for the National Coal Board until his retirement in 1981. Mr Gecas has publicly admitted that he joined the battalion, went with the Germans to Byelorussia, and later wore German uniform and fought in Italy. But he says, if Jews were rounded up and killed, he had no knowledge of it. Mr Gecas has avoided making any public comment since a libel action he brought two years ago against Scottish Television failed.