There is something that does not add up in Apple's discourse at http://www.apple.com/customer-...
Specifically, the FBI wants us to make a new version of the iPhone operating system, circumventing several important security features, and install it on an iPhone recovered during the investigation. In the wrong hands, this software — which does not exist today — would have the potential to unlock any iPhone in someone’s physical possession.
The FBI may use different words to describe this tool, but make no mistake: Building a version of iOS that bypasses security in this way would undeniably create a backdoor.
I read what the FBI asks as: install a piece of code that allows the phone's content to be examined. I see no middle ground between
1) running such piece of code (probably: after getting it signed by Apple) is possible without the owner's passcode; the iPhone is in fact already backdoored, with Apple holding the key, the FBI wants Apple to exploit the vulnerability/open the backdoor, and Apple does not want to bow, because that's against their policy.
2) running a piece of code signed by Apple also requires he owner's passcode; then the solution pushed by the FBI just can't work.
If the facts where 2, Apple could just state this to the FBI, showing the source code as proof. The FBI would have no choice but take it as fact (perhaps they would ask a change in the future, but it would not help immediately for this iPhone). I conclude the true story is 1, and Apple slightly misrepresents things stating the FBI wants the creation of a backdoor, when there's already one, only well locked and never previously used for nefarious purposes.