...fingerprint scanners don't work if the finger to scan from is dead.
Capacitive fingerprint scanners (i.e. the type found on laptops) work based on electrical difference. If there's no electrical difference (as would be the case if the finger was severed), the scanner won't work.
Practically-speaking, a person using a fingeprint scanner would (hopefully) use a random finger (rather than defaulting to the index finger) when registering, so one of these pesky terrorists would have to take *all* the fingers (perhaps in a purse of some kind) with him to make it work.
So there would be a man standing in the lobby of one of the most secure buildings in the country, fishing fingers (HAH!) out of his bag and trying them one by one while security looks on?
Typical Daily Mail slow-news-day bollocks.