Something that has been bugging me for some time is that my iPhone, normally unlocked with Touch ID, asks for my passcode way more often than it ought to. That mystery has now been solved by a bullet-point that Apple added to its iOS Security Guide earlier this month – though the behavior has been there a lot longer.

Previous versions of the document said that iOS devices should only ask Touch ID users for their passcode in one of five circumstances. I found I was frequently asked for my passcode when none of these applied, but a sixth, recently-added bullet-point explains it …

MacWorld spotted the change when seeking to answer a reader question about it. The additional bullet point is highlighted in bold below.

The passcode can always be used instead of Touch ID, and it’s still required under the following circumstances:

  • The device has just been turned on or restarted.
  • The device has not been unlocked for more than 48 hours.
  • The passcode has not been used to unlock the device in the last six days and TouchID has not unlocked the device in the last eight hours.
  • The device has received a remote lock command.
  • After five unsuccessful attempts to match a fingerprint.
  • When setting up or enrolling new fingers with Touch ID.

So, lock your iPhone or iPad and go to bed, and if it’s more than eight hours before you unlock it in the morning, you’ll be asked for your passcode.

Apple has not explained the reason for the change, but it may be in response to court rulings that have compelled suspects to use Touch ID to unlock their iPhones. The Fifth Amendment means that nobody can be compelled to reveal their passcode, but two separate courts have ruled that there is no protection against providing a fingerprint to unlock the phone.

The first was a Virginia District Court in 2014, while the first federal ruling on the matter was reported earlier this month.

The change in behavior will add urgency to cases where law enforcement authorities want to gain access to an iPhone: eight hours after it was last unlocked, compelling the owner to use their fingerprint to unlock it will no longer be an option.

The FBI recently warned that the resolution of the San Bernardino case does not end the matter, and that there will be more litigation on phone encryption to come.

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