For some reason, Dolohov's defense was "the Goblins made him do it'. Hoping to get him sent to Azkaban for life in prison now included disproving his assertion, else it risked him being released as part of a mistrial. When the Chief Warlock of the Wizengamot asked for a representative of the Goblins to step forward, Harry saw the flaw in the plan. Was this a setup? He didn't think that an imprisoned Death Eater could orchestrate any kind of break-out with Goblin help, but every assumption he had made before about the Goblins had cost the war effort dearly.