Gecas' lawyer, Nigel Duncan, said the crimes happened so long ago that the Scottish courts have to decide whether extradition is really appropriate.
"A matter that will again have to be considered is the amount of time which has passed, not only since the alleged acts were committed, but also since the knowledge of them was before the Lithuanian government," he said.
The BBC reported his lawyers are considering a challenge against possible extradition under the Human Rights Act, and might claim Gecas would not receive a fair trial in Lithuania.
Duncan told The Times he had not heard anything from the Scottish Executive yet. The Executive also refused to confirm that it had received the extradition request.
Lithuania's Prosecutor General, which brought charges against Gecas, reported it has prepared the additional explanations requested by the Scottish government and passed them on to the Lithuanian Justice Ministry, which in turn will send them to Great Britain.
"We are keeping in contact and are prepared to do everything necessary to administer justice," Prosecutor General press representative Vidmantas Putelis told Baltic News Service.
Last week the Scottish Executive came under fire from all sides for apparently dragging out the extradition.
Nigel Duncan accused it of keeping his client in the dark, while the Nazi-hunting Simon Wiesenthal Center demanded Scotland's government to explain why it was delaying making a decision on whether to fulfill Lithuania's extradition request.
Director of the Jerusalem branch of the Simon Wiesenthal Center Dr. Efraim Zuroff told the BBC he could not understand the reason for the delay and he feared Gecas might escape prosecution by claiming old age and infirmity.
Lithuania's ambassador to Great Britain, Justas Paleckis, handed Lithuania's extradition request to British home secretary Jack Straw on March 29.
The request was supposed to have been sent on to Scotland's Executive in Edinburgh, whose ministers were to have made a decision whether to begin extradition proceedings.
Lithuania used the 1957 European Convention on Extradition to request Gecas be sent home to face trial. The suspect is alleged to have committed crimes defined in the Lithuanian criminal code as genocide and the murder of people protected by humanitarian law.
Gecas, or Gecevicius, is suspected of taking part in Nazi attacks on civilians in occupied Lithuania and the Belarusian SSR when he served on a police force loyal to the Nazis.
Back in February the Vilnius 2nd Area Court issued a warrant for Gecas' arrest. The warrant was a precondition for requesting his extradition.
A Scottish court in 1992 established that Gecas led a division of the Lithuanian Auxiliary Police Battalion under Nazi command during World War II. The battalion's divisions took part in Nazi atrocities committed against Soviet partisans and ordinary civilians in occupied Belarus and Lithuania.
Gecas insists he committed no war crimes and never killed anyone.
The Lithuanian Prosecutor General is currently investigating upwards of 90 cases of genocide committed against Lithuanian citizens. Cases against 15 have gone to court in Lithuania so far.