Can Body Temperature Affect Breath Test Results?

Law enforcement DUI investigation techniques depend largely upon the fictitious premise that all humans are physiologically identical. Without that presumption, field sobriety and breath alcohol tests would not be possible. There are, of course, many examples of physiological differences — from person to person and within one person from moment to moment — which will directly alter breath or blood alcohol testing in DUI investigations. A few examples are diabetes, GERD (acid reflux), anemia — even sex and race create differences.

Yet another example of variability in DUI breath testing is body temperature. Put simply, an individual’s body temperature will have a direct effect on the results of a breath test. The effects of changes in body temeprature from the norm of 98.6 degrees on breath testing has been discussed in an article entitled “Body Temperature and the Breathalyzer Boobytrap”, 721 Michigan Bar Journal (September 1982). If because of illness, for example, the body temperature is elevated by only 1 degree Centigrade (1.8 degrees Fahrenheit), the 1:2100 breath-to-blood “partition ratio” (the ratio between alcohol in the blood and alcohol in the breath) will be affected so as to produce a 7 percent higher test result. Higher body temperatures will, of course, result in greater errors.

You don’t have to be sick to have a higher body temperature. Dr. Michael Hlastala, Professor of Physiology, Biophysics and Medicine at the University of Washington, confirms this — and the effects on DUI breath test results. In an article entitled “Physiological Errors Associated with Alcohol Breath Testing”, 9(6) The Champion 18 (1985), he comments that even the average body temperature of a normal, healthy person “may vary by as much as 1 degree Centigrade above or below the normal mean value of 37 degrees Centigrade — or 1.8 degrees from the mean value of 98.6 degrees Fahrenheit”.

Not only can the normal mean body temperature of an individual vary from that of other persons, but the “temperature of any individual may vary from time to time during the day by as much as 1 degree Centigrade”. Result? The partition ratio for alcohol in blood is altered — meaning, according to Professor Hlastala, a 6.3 percent error for every 1 degree Centigrade increase or decrease from the presumed normal body temperature.

Yet another example of how breathalyzers in DUI investigations are not actually testing you, but rather an “average” person who does not exist.

About the Author. A former Marine and graduate of the University of California at Berkeley (1966) and the UCLA School of Law (1969), Mr. Taylor served as a Los Angeles Deputy District Attorney and Independent Special Prosecutor before turning to private practice. He was a member of the faculty of Gonzaga University School of Law, where in his second year he was voted “Professor of the Year”, and was later appointed Fulbright Professor of Law at Osaka University in Japan.

Lawrence Taylor is also the author of over thirty articles and 12 books, including the standard textbook on DUI litigation, “Drunk Driving Defense”, 7th edition (co-authored with Steven Oberman) and “California Drunk Driving Defense”, 4th edition. Over the past 30 years he has proven a popular lecturer on trial tactics and techniques at over 200 legal seminars in 41 states. He was one of the original 10 founders of the National College for DUI Defense, later serving as its Dean. On July 25, 2002, at Harvard Law School, Mr. Taylor was presented with the College’s “Lifetime Achievement Award”.

Mr. Taylor currently limits the practice of his 4-attorney Los Angeles DUI law firm to drunk driving defense exclusively. He may be contacted at 888-777-3449, or his website may be viewed at www.duicentral.com.