Breathalyzer Source Code Required for Use as Evidence

Posted on: January 21, 2009 9:30 AM, by Ed Brayton

Here's a very interesting case from Florida, where an appeals court has upheld a lower court ruling that threw out evidence from a breathalyzer test in a drunk driving case because the manufacturer of the device refused to release the source code and allow defense experts to analyze the accuracy of the machines.

The results of breath tests in more than 100 local drunken-driving cases will not be allowed at trial, a judge announced Tuesday.

The validity of those breathalyzer tests has been challenged for more than three years because of the Intoxilyzer 5000, a machine that uses a breath sample to measure a person's blood-alcohol content.

Manatee County Judge Doug Henderson ruled two years ago that any Intoxilyzer 5000 tests were inadmissible in trial, but prosecutors appealed. On Tuesday, Henderson told lawyers that his ruling had been affirmed by the Second District Court of Appeal and Circuit Court.

Breath analysis machines are notoriously inaccurate and this has been a problem for a very long time. Dr. David Hanson, a sociologist who has written on this issue for decades, writes:

Breath analyzers (Breathalyzer, Intoxilyzer, Alcosensor, Alcoscan and BAC Datamaster are common brand names) don't actually test blood alcohol concentration (BAC), which requires the analysis of a blood sample. Instead, they estimate BAC indirectly. Different types of machine use different techniqes and larger machines generally yield better estimates than do hand-held models. Therefore, some states don't permit data or "readings" from hand-held machines to be presented as evidence in court. South Dakota does not even permit evidence from any type or size breath tester but relies entirely on blood tests to ensure accuracy and protect the innocent.

A major problem with some machines is that they not only identify the ethyl alcohol (or ethanol) found in alcohol beverages, but also other substances similar in molecular structure. Those machines identify any compound containing the methyl group structure. Over one hundred compounds can be found in the human breath at any one time and 70 to 80 percent of them contain methyl group structure and will be incorrectly detected as ethyl alcohol. Important is the fact that the more different ethyl group substances the machine detects, the higher will be the false BAC estimate.

The National Highway Traffic Safety Administration (NHTSA) has found that dieters and diabetics can have acetone levels hundreds and even thousand of times higher than that in others. Acetone is one of the many substances that can be falsely identified as ethyl alcohol by some breath machines.

One investigator has reported that alcohol-free subjects can generate BAC readings of about .05 after eating various types of bread products.

Substances in the environment can also lead to false BAC readings. For example, an alcohol-free subject was asked to apply a pint of contact cement to a piece of plywood and then to apply a gallon of oil-base paint to a wall. The total activity lasted about an hour. Twenty minutes later the subject was tested on an Intoxilyzer, which registered a BAC of .12 percent. This level is 50% higher than a BAC of .08, which constitutes legal intoxication in many states.

Similarly, a painter with a protective mask spray painted a room for 20 minutes. Although a blood test showed no alcohol, an Intoxilyzer falsely reported his BAC as .075.

Any number of other products found in the environment can cause erroneous BAC results. These include compounds found in lacquers, paint removers, celluloid, gasoline, and cleaning fluids.

Other common things that can cause false BAC levels are alcohol, blood or vomit in the subject's mouth, electrical interference from cell phones and police radios, tobacco smoke, dirt, and moisture.

Breath testers can be very sensitive to temperature and will give false reasings if not adjusted or recalibrated to account for ambient or surrounding air temperatures. The temperature of the subject is also very important. Each one degree of body temperature above normal will cause a substantial elevation (about 8%) in apparent BAC.

Many breath testing machines asume a 2,100-to-1 ratio in converting alcohol in the breath to estimates of alcohol in the blood. However, this ratio varies from 1,900 to 2,400 among people and also within a person over time. This variation will lead to false BAC readings.

Physical activity and hyperventilation can lower apparent BAC levels. One study found that the BAC readings of subjects decreased 11 to 14% after running up one flight of stairs and 22-25% after doing so twice. Another study found a 15% decrease in BAC readings after vigorous exercise or hyperventilaion.

Some breath analysis machinnes assume a hematocrit (cell volume of blood) of 47%. However, hematocrit values range from 42 to 52% in men and from 37 to 47% in women. A person with a lower hematocrit will have a falsely high BAC reading.

It's about time a judge took a stand on this issue.