Flawed drug test mistakes cheese for cocaine

Scotsman
Dec. 20, 2005

AN INTERNATIONALLY recognised test for cocaine is flawed - and can throw up positive results from powdered milk and parmesan cheese, say scientists. Laboratory research shows that the "Scott test" can fail to detect the drug in some samples and can wrongly identify it in some substances where no cocaine is present.

The test, introduced in 1973, is used by many police forces as a preliminary check on substances they suspect to be cocaine. A positive result is not enough to secure a conviction, but can lead to suspects being detained until a forensic laboratory completes a detailed analysis using mass spectrometry.

An alternative, more expensive test is used by some police forces, but the United Nations' field manual for drug-testing continues to recommend the Scott test, reports the magazine New Scientist.

The test involves three steps. If cocaine is present a blue precipitate should appear in the first step, disappear in the second and reappear in the third.