Using a thief to catch thieves?

[Philippus Flavius Homovallumus]

Not of a crime...if the German government intended to prosecute the tax-evaders as suspects of a crime, the evidence would be inadmissible. It can, however, be used to prove that they still owe the government taxes.

If they arrested someone for breaking into a bank computer and discovered evidence of other felons' tax-evasion on the hacker the evidence for tax-evasion would be inadmissable?

If that was true Al Capone would never have been convicted!