Breath Testing

Breath testing is one of the most common ways that Middletown police officers will try to determine if a person is driving under the influence of alcohol. As such, it is important to understand the breath testing process and the science and reasoning behind using this test. On this page, you can learn more about breath testing as well as ways in which you can defend against a failed test.


When driving in Middletown, you may be subjected to breath testing after a DUI arrest. Middletown law enforcement use breath test machines, often called breathalyzers, to obtain scientific evidence of the amount of alcohol in the person’s blood. They do this in order to strengthen the case against that person for driving while intoxicated. These machines work by exhaling into a device with a small mouthpiece for a certain amount of time. While traveling through the device, the air molecules pass through beams of infrared light.

Henry’s Law

These breathalyzer devices are based on the science called Henry’s Law, which is defined as the “mass of gas that dissolves in a definite volume of liquid which is directly proportional to the pressure of the gas provided that the gas doesn’t react with the solvent.” In other words, if the gas and the liquid are contained in a closed space together, the concentration of the gas to the air above the liquid is the same as the gas dissolved in the liquid itself. One way to visualize this is by thinking about an amount of blood inside a container, where the blood evaporates until the concentration in the air above the blood is equal in concentration.

Within Henry’s Law, there is Henry’s constant, which is the ratio of the blood in the human body to the air, which is measured by a ratio of 2100:1. This means that on average, the concentration of alcohol in the blood is about 2100 times greater than the air.

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Problems With Henry’s Law and BAC Testing

This leads us to ask the obvious question, which is how can there be the same “constant” that is used to test the blood alcohol concentration in everyone? This is precisely the problem with the accuracy of the breathalyzer because each person differs in size, weight, and physical makeup, leading to an estimated 0.03% or greater error in every breathalyzer.

Further, body temperature can play a huge role in the reliability of the breathalyzer results, as even a slight change in body temperature can totally alter the blood alcohol concentration. Something as simple as taking a large dose of aspirin can alter the concentration in the body as well. Other issues such as diabetes, illness, and medications can alter the results of the breath test.

There is also the possibility that issues within the breathalyzer itself exist. Issues are usually caused by either poor maintenance or improper calibration of the device. The devices must be calibrated on a consistent, fixed schedule. The officer administering the test must be trained and certified in using and administering the device because there is a certain procedure that must be followed to ensure higher reliability in the results.

The administrator must also be sure that their test subject has not burped, vomited, eaten, or smoked immediately prior to the test because those are all things that can alter the breath sample. Lastly, breath results are reliable only when it captures two results in measurements that are within .02 of one another.

Breath Testing Penalties

There is a law in Connecticut, called the Implied Consent law, that means every person implicitly consents to a breathalyzer to test their blood alcohol concentration when they get behind the wheel. Everyone, however, is still free to decline to take the breathalyzer despite the consequences, one being a lengthy license suspension.

It is a personal decision that requires weighing the potential consequences of a license suspension and the consequences of having breath test results admitted as evidence in the criminal DUI case. A good DUI lawyer will be able to determine what possible defenses and problems with a case exist and use those to benefit her client. If you are facing a DUI charge in Middletown, consider contacting Lady DUI to find out how we can help.

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