iOS Tip 169 - Disable Fingerprint Unlock

Your Touch ID or fingerprint sensor is meant to keep your data more secure. But in some cases federal agents can force you to unlock your phone with your fingerprint, because the courts have determined that it's not a violation of the Fifth Amendment, which protects against self-incrimination. The feds however can't force you to turn over your passcode.
Turn off Touch ID by going to Settings > Touch ID & Passcode > turn off iPhone Unlock.