Sir, Drug testing, in US schools and in the workplace, is based on faulty logic.  It invades the privacy of millions in order to detect thousands - most of whom are casual marijuana users.  If we were to disqualify from public office anyone who had ever smoke marijuana, we would lose at least one presidential candidate; Congress and the courts would be much diminished; and almost 50 per cent of Americans between the ages of 20 and 50 would be banned from public office.

Second, drug testing easily becomes a surrogate for good management, distracting attention from the many other factors that can impair employee performance, including sleep deprivation and poor morale.  Furthermore, most drug testing reveals much more about what a person consumed last night or over the weekend, and little about whether they are impaired at work.  And - bizarrely - if you want to pass a urine test on Monday morning, it is "safer" to take cocaine and alcohol than to smoke a joint the Friday evening before.

We started with military personnel and airline pilots.  Now we are testing millions of civilians who work at desk jobs, and the surveillance salesmen have their sights set on our children.  It's the same old logic, driven by an industry that reaps billions in profits from sales of the latest drug-detection systems.  I wonder when people will finally say "enough".  When drug testing starts to include nicotine products? Or undesirable food products? Or when employees who test positive are required to take a pill designed to make them sick the next time they consume a prohibited substance?

Most drug testing programmes do more harm than good.  When and where will we draw the line?

Ethan A.  Nadelmann, Director, The Lindesmith Center, 400 West 89th Street, New York, NY 10019, US