Amit Mathur, founder and former president of Entrust Capital Management of Worcester, was convicted last May

Amit Mathur, founder and former president of Entrust Capital Management of Worcester, was convicted last May. He wants a new trial and is challenging the credibility of a primary witness.Assistant U.S. Attorney John Capin has filed a motion opposing the bid for a new trial, saying Mathur’s arguments show his "continued refusal to accept responsibility."Investigators say Mathur used the $13 million to cover trading losses and personal expenses such as jewelry and a Porsche sport utility vehicle. He is being held in a federal detention facility in Rhode Island while awaiting his scheduled May 11 sentencing.