When talking about biometrics, for it to work perfectly there should be at least two out of three things: something you know, something you are, something you have. It can be a card you swipe (something you have ) and password (something you know). When creating employee database you have certain number of employees the information has to be checked against, there can be no other person except the ones in the system, ideally anyways. When looking for the terrorist in the crowd of people is a whole different story. The system is looking for one known person it the enormous pool of unknown subjects. They are in luck if they have at least one valid photo. This is time consuming and not very effective, even thou it sounds like a great idea.
Of course the employee database is more reliable, as it is matching one person against the pool of the people that are well measured and photographed. As opposed to searching for a person we know in the thousands of unknown people. Even name or birthdays cannot be compared as we don’t know who they are and what are their birth dates respectively, this is very close to looking for a needle in a haystack. Talking numbers, assume that one in ten million flyers, on average, is a terrorist. If there is 99.99 percent chance that the person is a terrorist, there is also a 99.99 chance that the person can be “not terrorist “, and with the stats given above it means that for one real terrorist alarm there will be 1000 false alarms. This is under condition that the photo of the person of interest will be just perfect, not taken form 1000 yards away with a beard which is now gone.
The EFF is concerned about fingerprinting as a part of biometric system. First of all fingerprint can easily be grabbed without permission of the owner. Secondly, fingerprinting is used extensively in criminal justice system. If two databases were to unite, this would provide government to do major tracking of individuals, which will be great invasion of privacy people did agree to.