I am prosecuting a case with a rather high breath result. The defense attorney has produced medical records showing the defendant's body is incapable of producing red blood cells. The defendant requires a complete transfusion every 3 weeks. The supervising technician says that calibration of the Intoxilizer 5000 includes the variable of a normal hematocrit level (volume of red blood cells). The defense attorney argues that if the hematocrit level is below normal the breath results will be inflated. While I have a decent impairment case I was wondering if anyone has addressed this question regarding the scientific side of the case.

Sure seems like a person who needs a blood transfusion every 3 weeks should be avoiding drinking alcohol, regardless of the amount.

Thompson, RQ "The Thermodynamics of Drunk Driving", J. Chem. Educ. 74,1997:532536

calculated uncertainty for 'normal' hematocrit levels is 6.4%. Presumably the defendant will aruge that his hematocrit levels are outside normal, and thus there is even greater uncertainty over the possible variation. I have no idea if the effect of hematocrit on blood alcohol measurements can be extrapolated linearly, or what blood replacement typically does to hematocrit levels. I doubt that there is a simple answer.

The simple answer is to stop drinking and driving.

Tell the defense attorney you're willing to consider his argument if his guy will submit to another breath test. Then see what the results are. Make him bring in his medical records and do it roughly the same amount of time after his last transfusion as when he blew the first time.

How is he arguing the BAC is "inflated?" The statute defined intoxicated as having a breath alcohol concentration over .08--having a medical reason why your breath would be at .08 when someone else might not is no defense. He would have to show that his BAC was in fact UNDER .08 to have a defense--he can't just whine that he has a medical condition that makes it easier for him to reach that level.

The breath meachine doesnt directly measure alcohol in your breath, it is a spectrometer so it measures the absorbtion of certain wavelengths of light and then extrapolates the amount of alcohol from those measurements.

The operator of the breath machine is saying that the calculations include certain assumptions about the defendant's blood.

The defense attorney says that those assumptions are not valid for this defendant because of an unusual medical condition. If the assumption is invalid then so is the calculation.

So the defendant might not have been intoxicated but the breath machine said he was because of an invalid assumption that would have been correct for most people, just not for the defendant.

Does the defensre really know it would inflate the score or is that just an assertion? Does the machine operator agree? I mean, couldn't something that goes against the built-in assumptions also deflate the score?

Having a low hematocrit means a higher proportion of plasma in the blood. Alcohol is more soluble in the plasma, so adding alcohol to blood will result in higher BAC in samples with low hematocrit. In other word, an accurate BAC level will be higher in a person of low hematocrit than for a normal person who ingested the same amount of alcohol. This theory only explains why low-hematocrit people should avoid alcohol, it has nothing to do with causing errors in their breath testing.

The "assumptions" made by the Intoxylizer are not all that relevant, if the assumptions only relate to equating breath AC with blood AC. The the partition ratio of 2100:1 (the "assumption" I think is referenced here) is important if you are concerned with estimating blood concentration from a breath sample. But our statute does not require us to equate the breath test to a blood result. It defines intoxication with reference to the breath concentration itself.

Unless this medical condition results in the presence in one's breath of something that the intoxylizer erroneously reads as alcohol (which I find hard to believe) then the instrument is properly measuring the amount of alcohol in the breath. A medical reason for having a high alcohol concentration does not negate the fact that you have a high concentration, it corroborates it.

Right the statute specifies a breath concentration, but it isn't that simple. There are some exceptions due to the limitations of the machine. For example the machine can't give good results if the driver drinks more alcohol or vomits immediately before giving the sample. These things may lower the reliability of the machine's calculation.

If extra alcohol in the mouth might upset the machine output then might extra alcohol in the plasma do the same? Just thinking out loud here but with reduced blood cells, the circulatory system would need to pump a higher volume of plasma through the lungs to get the same amount of oxygen as compared to a normal person. So a breath taken by this individual would be exposed to more plasma than a breath taken by a normal person. I'm not saying it's true, just plausible.


Bottom line is trouble if the machine operator testifies that the machine is not calibrated for someone with this medical condition... unless the operator also says the machine would under-report for somebody in this situation. This seems like a good time to cover the driver's loss of normal use.

I would be inclined to feel sorry for someone that has to have their blood drained/refilled more often than the oil in their car. That would change if he was actually impaired and dangerous.

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Originally posted by AlexLayman:
If extra alcohol in the mouth might upset the machine output then might extra alcohol in the plasma do the same? Just thinking out loud here but with reduced blood cells, the circulatory system would need to pump a higher volume of plasma through the lungs to get the same amount of oxygen as compared to a normal person.

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You are making the same mistake again. The law prohibits driving with a certain amount of alcohol concentration in the breath. The reason the alcohol in your mouth invalidates the result is because that is not lung alcohol, and therefore will prevent a valid reading in the intoxylizer by throwing off the slope detector. Such a result is not invalidated because the alcohol causes an erroneous result: it is invalidated because the instrument accurately measures an alcohol concentration that is inconsistent with exhaled lung air, which should increase in concentration until it levels off as the deep lung air is expelled from the lungs. Alcohol in the mouth will register as a high concentration followed by a drop off. The instument reads these amounts correctly, but invalidates the sample as being inconsistent with the deep lung air that we want to measure.

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Bottom line is trouble if the machine operator testifies that the machine is not calibrated for someone with this medical condition

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While you may be right on that, I think the technician may be using a misleading term there. The instrument is not calibrated for any particular medical condition. One could argue that the .08 level we use was selected based on certain "average person" equivalencies between breath and blood, but I fail to see how the mechanism used by the Intoxylizer could report a falsely high result due to a medical problem in the person providing the sample.

It may be that your technician is suggesting that the instrument does not adjust the measurement to account for hematocrit levels, or unusual partition ratios, or the like. If so, there is nothing erroneous about the results, they just may be more or less valuable in estimating the blood alcohol level.

I would ask your defense attorney whether he has an expert who will be willing to testify that the breath of a person with a low red cell count will register in the Intoxylizer as containing more alcohol than is truly present. I seriously doubt it.

The explanation makes sense on a technical level but the statute doesn't mention "lung alcohol" or slope detection.

Logic that excludes mouth air from "breath" could also exclude plasma from "blood".

Alex--
The mouth alcohol generally dissipates within 15 minutes of the last drink, and only becomes a factor as mentioned if someone vomits, etc. This is what the 15-minute waiting period is for. The instrument is designed to detect deep lung breath. In a DWI trial, there is almost always testimony on these issues. I hope that alleviates some of your concerns!