From the article:
It was important to Doherty that the casting of Moriarty be kept secret for as long as possible. "We're approaching very carefully and as quietly as we can. At the end of the day, we want a tremendous actor," he said. "It's less fun for me if you know who he is."
Then why, Mr. Doherty, do you always cast a name actor as the murderer and thus give the game away right off the bat???!!!!