Unfortunately, many DWI attorneys don't understand the science behind the tests that are administered, both the Breathalyzer and the Field Sobriety Test. While it isn't necessary to be terribly technically oriented, to be a good DWI lawyer they MUST understand how and why certain conditions other than alcohol could cause "false positives", although that really isn't a correct designation.
Diabetes is one of the conditions that can cause an uneducated police officer to believe a person is intoxicated when they are not. There are a couple of reasons for this which I'll discuss in a little more detail. To make it easier to understand, I'll start with the police officer seeing a car that is weaving.
As the police officer follows the vehicle the camera in the police car will be recording, showing the vehicle failing to stay in its land and operating erratically. When the police officer activates the lights and the siren, the video will also show it takes longer than it should for the driver to realize they are being stopped, and longer to pull over than is reasonable.
The audio tape that is being recorded from the officer's lapel or shoulder microphone will record the driver's slurred speech. As the driver exits the car they may be unsteady on their feet, their attitude belligerent.
They are unable to pass the field sobriety tests and, despite their protestations that they have not been drinking, the driver is handcuffed and taken to jail, where they fail a Breathalyzer test, registering above the .08 which is the legal level in all states.
At trial the driver produces two witnesses who testify that he had just left their house, where he had been helping them with a project all day, and had not been drinking. Despite the testimony, the jury relies on the "objective" findings of the Breathalyzer and the field sobriety tests, and convict the driver.
There was no evidence offered as to the driver's diabetes and how it can affect the tests administered by the officer as well as the driver's behavior. No evidence that it was something other than alcohol which caused symptoms of irregular behavior to be clearly visible to the jury.
For diabetics, low blood sugar (hypoglycemia) or high blood sugar (hyperglycemia) can mimic the effects of alcohol.
This problem is getting worse in the U.S. Whether you agree there is an obesity epidimic or not (and obesity is a cause of diabetes) the number of diabetics in this country is increasing, with more than 18 million people in the U.S. currently suffering from the disease, many of them undiagnosed.
Low blood sugar (actually low blood glucose) can experience dizziness, slurred speech, muscle weakness, confusion and loss of coordination. High blood glucose symptoms include blurred vision and excessive fatigue or sleepiness. It is clear just from reading these symptoms how an officer who already has a predisposition toward the intoxication of a suspect could misinterpret these symptoms. It is also clear that these could have a dramatic effect on the ability to pass field sobriety tests, which are difficult even when sober under field conditions.
What about the Breathalyzer test?
We'll assume for a moment that Breathalyzers are accurate (and that is not necessarily true). The science behind the test explains why a diabetic might get a reading that is technically correct, but absolutely no indicator of alcohol intoxication. The machines work because of infrared spectrometry, that is, they shoot a beam of light through the breath sample provided and analyze how the light is absorbed or blocked by the various compounds in the breath.
The breath of a diabetic can contain acetones if the diabetic is experiencing ketoacidosis*, resulting from a shortage of insulin. In response to the ketoacidosis the body begins burning fatty acids, which produce ketones and the body tries to rid itself of these by excreting the ketones/acetones in the breath. The Breathalyzer reads these the same as alcohol, thereby producing a reading that is above the .08. Unfortunately, the machine can't differentiate between the two.
It is important for a defendant to let the defense attorney know if they have diabetes and also to insist, and be prepared to pay for, proper evidence to prove that this was more likely to have been the cause of the test results.
* People on low carbohydrate diets are also susceptible to a false breathalyzer reading as the concept works the same.