Mr Schreiber is accused in Germany of evading taxes on millions of dollars from commissions for arms deals.
He was also at the centre of a scandal surrounding the funding of Helmut Kohl's Christian Democrat Party, the CDU.
The scandal began with the emergence of a series of undeclared contributions given by Mr Schreiber.
Mr Schreiber, who has both German and Canadian citizenship, was arrested under a German warrant in Canada in 1999. He was released on bail in 2007.
In a separate, Canadian case, he has been testifying at a public inquiry about his financial dealings with that country's former Prime Minister, Brian Mulroney.
Mr Mulroney has acknowledged taking C$225,000 (£125,000) from Mr Schreiber in return for promoting a project for a German company, though he denies Mr Schreiber's claim that the money was exchanged while he was still in office.
Public hearings on the case ended last week.