@ AC above
There hasn't been a biometric technology ever released where the inventors thought about who *couldn't* use it. The industry measures biometrics, at least in part, by the Failure to Enrol Rate (FTER) - that is, the percentage of people who could not put the biometric (whichever it is) on the system. However, they NEVER include people who do not have whatever bit of body is needed (finger, eye, whatever) - this is the "outlier" population, members of which are referred to as "goats". The FTER only includes those who *have* the relevant bit, but couldn't enrol ...
... Oh, and then governments buy them for major rights-affecting applications like ID cards and passports without realising (or caring) that they haven't been tested on people that have no way of using them.