17 Dec
2003
17 Dec
'03
11:17 p.m.
Two ways to tell if the person has had the test: A) The company performing the test keeps track of everyone who has had it. This could be by some biometric ID, perhaps even a DNA fingerprint. B) The company performing the test marks people who have had it. They could have a harmless radioactive tracer injected. This would degrade after a while but it could be used to see if the test had been taken within some time interval. Both of these require that all companies able to issue the test cooperate and that there is no black market source of testing.