In fact, researchers have concluded that using a single venous blood sample to determine an earlier blood-alcohol concentration produces a result that is equivalent to a wild guess. In an article entitled The Pharmacokinetics of Alcohol in Human Breath, Venous, and Arterial Blood After Oral Ingestion, Martin, et al., 26 European Journal of Clinical Pharmacology 619 (1984), scientists measured comparative BAC levels in the breath, arterial blood, and venous blood of subjects who had consumed known quantities of alcohol.
The researchers noticed that BAC of arterial blood was higher than that of venous blood during the absorptive phase that is, while the alcohol was being absorbed by the body. Conversely, the venous samples had higher blood-alcohol levels than the arterial samples during the elimination phase of the blood-alcohol curve. Thus a venous blood sample taken during the elimination phase will be analyzed as having a higher BAC than is in fact being carried to the brain.
The conclusion of the scientists was that a venous blood sample does not accurately reflect the amount of alcohol entering the brain and so is not indicative of the true degree of intoxication.
Los Angeles DUI attorneys should review their jurisdiction’s statutory or administrative language concerning blood analysis and determine whether there is a requirement that the sample be arterial or venous blood. If one source is specified, the prosecution should be required to lay an evidentiarv foundation as to the actual source for the sample. It is not uncommon for the technician or nurse withdrawing the sample to be unable to specify or recall whether an artery or a vein was tapped, other than to say what their usual practice is.