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From: Robert Swotinsky MD
Date: 28 Oct 2004
Time: 07:18:32 -0700
Remote Name: 4.17.131.55
A number of states -- perhaps yours -- have passed laws under which a positive drug test is considered evidence of impairment. I agree with your MRO's comment that there is no connection between urine levels and an accurate determination of being "under the influence." Even though the scientific consensus is that drug tests (except when performed with blood) are poor measures of impairment, the statutory definitions nevertheless establish a legal basis for presumption of impairment and, in many instances, fault. A "presumption of impairment" means it's assumed the person was impaired and it's the person's burden to prove otherwise.
The cocaine metabolite level of 269 ng/mL tells us that the person used cocaine within 2-3 days of the test. There's one published study that presents graphs showing urine cocaine levels over time after certain doses [Ambre J. The urinary excretion of cocaine and metabolites in humans: A kinetic analysis of published data. JAT 1985;9:241-5]. But, it's not responsive to your question about equating urine drug levels with impairment. In fact, there's a number of scientific publications that state one cannot equate urine levels with impairment.