the real problem is cost, hair tests are roughly 3x the cost of piss tests and the only state that has shown them to be effective did so by people simply not showing up due to the fact they knew they would fail. if everyone was tested it would cost far too much money, let alone if there were random or multiple tests
I had no intent to suggest that drug testing hair samples for everyone was a viable answer. Simply offering another testing option to the list. An absolute source for testing that would extend the use range exponentially is to test vitreous, but that causes a problem in itself as we only do that post-mortem.
There are actually two types of testing for hair. Testing the follicle can cover 30 to 90 days, but collection of multiple hair shafts can cover a much longer period of time. If one shaves their head, body hair can be used and actually may cover an even longer period of time due to a slower growth rate. We used to collect hair samples for drug testing and would cut small samples to accumulate around 100 individual shafts of hair, so the follicle wasn't even involved in those.
I don't think any testing beyond the average urine and blood screens would be necessary. Those who are addicts are going to use no matter what and the random factor makes it difficult to overcome the testing. I've been involved in drug testing in one form or the other off and on for 15 years as a RN in several venues, and I have yet to see anyone successfully use any of the many reported cleaning or masking agents. Many times, we would either detect dilution of the sample or a metabolite of the agent itself.
I spent several years working for the Dept. of Labor providing medical care for the Job Corps program, and believe me, many of those kids would try anything to make a sample come up clean. We used to have boxes and boxes of confiscated Goldenseal, Flax seed oil, Acai, etc. None of them worked. Those that tried to dilute their urine would have values so out of whack it would look like they were in renal failure.