Michigan Blood Results - What is Gas Chromatography and how can you beat it in court?

In Michigan, blood samples are tested by the Michigan State Police; the MSP use the flame ionization gas chromatograph blood analysis process. This process is considered to be reliable, but it has sources of error, uncertainty, and must be performed in a scientifically acceptable way.

The prosecutor is required by the constitution to produce the witness who conducted the analysis of the blood sample. This blood sample is not the entire sample, but rather a small portion of it. This small amount of blood is combined with t-butanol and n-propanol. The mixture is heated and a needle draws what is known as the “headspace” from the vial.

Headspace is the gas space above the sample in a chromatography vial. Volatile sample components diffuse into the gas phase, forming the headspace gas. Headspace analysis is therefore the analysis of the components present in that gas.

The headspace is then blown into a gas chromatograph by carrier gas, which for the MSP is helium. The vial is capped with a buta rubber stopper that the needle punctures to draw the headspace gas from the mixture. There are studies available that say not to use this rubber stopper, because it could absorb the organic compounds in the vial , which would alter the mix, which would compromise the sample. If this rubber stopper absorbs the t-butanol or the n-propanol, then the alcohol concentration will be higher in the sample.

Along with the questionable use of the buta rubber stopper, the integrity of the concentration of the blood sample depends on the integrity of the vacuum seal of the initial blood collection from my client. Chemical solvents are used to maintain the blood from the point of the blood draw to the time when it enters the gas chromatograph process at the MSP lab. If this seal fails then the sample is contaminated.

The administrative rules used by the MSP lab are actually less stringent than the accepted scientific principles. One alarming lack of stringency is the use of one controlled sample throughout the entire day instead of before and after each sample. This means that the machine is only tested when the doors open; if the machine is malfunctioning or not producing accurate results by lunch time, you’re going to have a full afternoon of questionable results, which should not be used as evidence in a criminal case.


The MSP lab also does not follow the MIST 8-step protocol for use of an uncertainty budget aka sources of error. MSP’s explanation for not following the strictest protocols is practicality, which is not acceptable to me.