1) Why is Charles Darnay acquitted at his English trial?

When he first appears in the novel, Darnay is on trial in London, accused of passing information between France and England. When the court’s attention is drawn to Sydney Carton, the members realize that the two men are virtually identical to one another. The resemblance plants the seed of doubt about whether someone else could be mistaken for Darnay. As the result of this possibility, and the circumstantial evidence, Darnay is acquitted and allowed to go. The trial even turns out to have been a positive event for Darnay, because it puts him back in contact with Lucie and Dr. Manette.