The chance of false match on fingerprints is actually quite small, but we don't know how they are using the tool. In the US, a fingerprint match has to be verified independently by two certified fingerprint examiners before some action is taken. I don't know how they are using it in Afghanistan, but from what I have heard it *is* a screening tool. If they get a match, they just detain the person until they can figure out out what the deal is. I suspect the rate of false positives is not all that high, otherwise the tool would be useless for checkpoints.
It's a trade-off. Do you reject all poor fingerprints so you can decrease your chance of a false match? If you do that, you are going to reduce the size of the database because a lot of people only have poor fingerprints. Using the face as a backup verification method is actually quite useful. The chance that two people are going to have similar fingerprints AND similar faces is quite low.
The US will share whatever is negotiated with the Afghans. Countries share varying amounts of data all the time, depending upon what they negotiate. The Afghans are not sharing *all* of the data they have, and the system is in place because the Afghans want it. If they didn't want it, they could force the US to remove it.
It was a fingerprint match, not a face match, although it is not clear from the article. The face is just there for secondary verification. In a false fingerprint match, you would expect the fingerprints to be similar, but not the faces.
Don't forget, the US paid for the system.
I'm curious - people are worried about the government having their biometrics. What specifically are you concerned about? What is the nightmare scenario that bothers you if the USG has your fingerprints? In case you haven't noticed, you leave your fingerprints everywhere; if someone wanted your fingerprints, it would be pretty easy to obtain them without your consent. Similarly, someone can collect your face biometric by taking a picture of you at the mall, or from your driver's license. I don't think there is any way to stop the spread of biometric databases, the same way it is impossible to stop the spread of stolen credit card numbers. We have to look at legislation centered around what people are doing with that information.
Biometric are about probabilities, and a poor fingerprint has a higher chance of a false match. Many Afghans have poor fingerprints because of manual labor (masonry work, etc.). Also, a miss is harder than a match, because you have to search every single record. They may have the thresholds set so low that the "best" match pops up, even if it is not a great match. That would explain this kind of false positive for the reporter. It sounds to me like the system worked - there was a secondary verification of using a photograph, which would have cleared the person who got the false positive.