Sirius in Azkhaban

[constance_vigilance]

No: HPFGUIDX 41915

I'm new and haven't gotten through all the archives yet to know if 
this issue has been raised, but my question is - 

Why did Sirius stay in Azkhaban those 12 years if he could transform 
into a dog and escape, apparently easily, at any time? 

He knew that Peter was alive and would have been motivated to clear 
himself and find Harry, who, as his godchild, he had an obligation to 
take care of.

The only possible reason I could think was to keep the Death Eaters 
from leaving the island to search for him and create havoc in the WW. 
Any other ideas?


SMiller