Think about Neville

[pippin_999]

Anne:
  That doesn't tell us anything about the person who did the
> sending, now, does it?  You may immediately imagine Lucius 
Malfoy, who *could be* in on the secret, sending the Lestranges 
after Neville's parents (remember that Lucius had some 
familiarity with the prophecy in OoP).<
> 


Pippin:
Lucius? But why make a big mystery out of him? We already 
know he's a DE. Besides, if he was the one who sent the 
Lestranges after the Longbottoms, then why did Voldemort chew 
Lucius out for not trying to find him? No, that "sent" is the biggest 
clue yet that Voldemort's shadowy second-in-command is  an 
undiscovered traitor to the Light. 

Pippin