Section 86 Determine Lab Error Rate on Entire Run of Gas Chromatography/Mass Spectrum

• Library: DWI Experts and the Science of Chemical Tests 2014

The crime lab director or witness will say that the GC/MS is accurate to +/- 5%. This is true some of the time. Often, if counsel, by way of discovery, gets the data from the entire run of samples and not just the subject, a higher error rate is shown. This is why, in discovery, counsel must insist and fight for the entire run of the GC/MS that contained the subject’s test. Error rates of 20%–30% are not uncommon. This is still less than breath testing error rates, but getting this data is significant to winning a case.

In a DWI (driving-while-intoxicated) case for 0.08% BAC, the following is how the error rates stack up:

5% Error 0.076% to 0.084% or 0.004%

10% Error 0.072% to 0.088% or 0.008%

20% Error 0.064% to 0.096% or 0.016%

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