I do not disagree with you, however I am sure the Melbourne police and public prosecutor are pretty sure of their case against Pell or else it would never have been brought.  They know full well that Pell is #3 at the Vatican and this action will be leading headlines around the world and the global media will follow it very closely. Indeed many of their careers are on the line if they cannot prove their case against Pell.  

As Ralph Waldo Emerson said, "If you strike at the king, you must kill him."