In the light of the serious consequences for the individual, and liabilities which can be incurred in the event of a positive or incorrect test result, Simpson et al[1] discussed the need for established procedures covering storage, chain of custody, confirmation of results and appropriate legal standards for "library" matching of spectra from unknown substances (e.g. designer drugs) requiring identification.

Most blood and urine tests for the presence of heroin differ from alcohol test results as these measure a metabolite of heroin (morphine) which is itself active. Heroin is metabolised to 6-monoacetyl morphine and then to morphine in the blood. Alcohol produces clear dose-related impairment as measured by breath, blood or urine tests. The presence of morphine in urine merely signifies that the person had used or been exposed to opiates at some point prior to the test.