what event leads to Darneys acquittal?

Carton looks so much like Darnay that a positive identification of the defendant is made impossible. Darnay's defense counsel, Mr. Stryver, shows that Barsad was himself a traitor. The jury deliberates for a long time. Lucie faints and is taken out of the courthouse. Mr. Lorry tells Jerry to remain to take the verdict to Tellson's. Jerry receives a piece of paper on which it is written that Darnay is acquitted.