Harry's Use of Cruciatus curse and why no one noticed

[kempermentor]

No: HPFGUIDX 109942

Cory wrote:
Another thing that bothered me almost as much, however, was how come 
his use of Cruciatus went so unnoticed by everyone?  The Ministry 
seems to know what Harry is doing 24/7; he was threatened with 
expulsion from Hogwarts for dumping his aunt's pudding in the floor, 
casting a Patronus to defend himself, and borrowing a flying 
car...but he casts an Unforgivable Curse inside the Ministry building 
and no one cares?
 
Any thoughts?

Kemper thinks:
Those incidents occur during summer holidays.  Maybe the Deparment 
that's in charge of monitoring magic of the underage takes a well 
deserved rest during the school year, focusing mostly on the antics 
of those witches and wizards aged 11 and younger.