Quote Originally Posted by Myrtle
Isn't it a coincidence that Snape randomly got the results for people who were alive at the time?
Yes, it is - but you should rephrase that to being "still alive now." If it was really random, he had a good chance of investigating someone who's now dead, and that would be a very easy out. Which just lends credence to my theory that Filch and/or Peter are also likely mafia, but Snape is the only certainty in my explanation.