What would happen if you downgraded an iPhone 5S to iOS 6?

Would Touch ID still work if you ever downgraded? If not, what would happen?

Touch ID is programed into IOS7 so no. It wouldnt work, as fair as my knowledge goes.

You can't downgrade ios on any idevice unless you have backed up your shsh blobs when your idevice still on older ios.
But since iphone 5s pre installed with ios 7 so i think its imposible to downgrade iphone 5s to ios 6