It was a stark question for any judge to ask in a criminal trial. Judge Roland Zickler, the presiding judge in a landmark fraud case, in a courtroom in Bonn, asked last week: “Do we all want to live in a world where everyone is ripping each other off?”  Last Wednesday,  one of the defendants in the trial one a Co Down-born investment banker called Martin Shields, discovered that the answer was no. Shields along with a fellow banker was convicted  of tax evasion in relation to so-called cum-ex trades in a ruling in Germany that had big repercussions for…