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High-tech fingerprint scanners may stop most thieves accessing a restricted area, but they have one fatal flaw: scanners can’t tell the difference between a finger that’s living or dead. Or

undead. Cases of robbers amputating a kidnap victim’s finger to get past biometric security systems (and perhaps a very natural fear of a zombie attack) have inspired scientists to examine

how to make scanners smarter. In a paper published in the journal _Forensic Science International_, German scientists report a breakthrough in what they describe as “liveness detection”.

“Differentiation of living fingers, fake fingers and fingers from dead bodies was investigated using spectral analysis,” the authors write. The scientists investigated how light was absorbed

by a living finger when it “blanches” or turns whitish as blood drains away when pressure is applied. Dead digits were also put to the test. “For this purpose, reflection and transmission

spectra in the wavelength region from 400 to 1650 nm were recorded from living volunteers and corpses,” the paper said. “The dynamic differences in the curves (including the absorption

changes caused by the blanching effect and the pulse) provide initial approaches for the realisation of systems for liveness detection. Significant differences that would be useful for the

integration into fingerprint recording systems of methods to defend against forgeries are discussed.”