What's our motivation?
What do we gain by clothing, feeding and interrogating an innocent taxi cab driver?
Are our techniques so poor that we cannot determine that the wrongfully accused person is an innocent taxi cab driver?
If he's an innocent taxi cab driver, why don't we just let him go and concentrate on non innocent taxi cab driver types?
We gain a few things:
1) Less burden on our troops...if we can dragnet and determine guilt later, then it is more efficient for the front lines.
2) Reduces chance of false negatives if we don't discard.
But please... decide which way to argue...are you claiming it's easy to tell the innocent from guilty, or impossible? Can't have it both ways.