Breath Testing

If pulled over and suspected of driving under the influence, the police might ask you to take a breath test. You can learn more about the science behind the breath testing devices on this page. Also learn about common issues with breath testing and how you can use this information to defend against breath test results in Hartford, Connecticut.


In Hartford, breath testing machines are a common tool used by law enforcement to test for the presence of alcohol on a person’s breath after a DUI arrest. When a police officer uses a breathalyzer device, they will instruct the arrestee to take a breath and then exhale air into the device through a small mouthpiece. The air goes into the device, and as it travels into the device, the air passes through a light source, similar to a bulb.

Henry’s Law

The breath analysis is based on a scientific law called Henry’s Law, 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.”

This means that if a gas and a liquid are confined in a closed container, the concentration of the gas in the air above the liquid is proportional to the gas that is dissolved in the liquid. This can best be related to a thought experiment in which blood is in a closed container that contains alcohol, and the alcohol will evaporate until the concentration in the air above the liquid is equal to that in the liquid.

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This is known as Henry’s Constant. The ratio given to that of the blood in the human body to be used in accordance with this law is 2100:1. The concentration of alcohol in the average person’s blood is approximately 2100 times as great as the concentration in the air with it.

Issues With Breath Testing

The problem is that a normal amount of blood/air equilibrium doesn’t exist. This is because every person’s body weight, frame, and physical makeup is unique. Scientists have determined that there can be up to a 0.03% error or more with each breathalyzer due to the normal ratio being used as a constant in the breath testing.

Not only can a person’s size influence the accuracy of a breathalyzer, but a person’s body temperature can also impact the results. An increased or decreased body temperature can increase the percentage of the blood alcohol concentration due to the volatility of alcohol. Taking a heavy dose of aspirin can even cause the body temperature to be reduced and potentially alter the breathalyzer results. Medical problems such as diabetes, sickness, and medication can all be possible defenses to the breathalyzer results.

Another factor that can seriously alter the accuracy of a breathalyzer is poor maintenance or improper calibration of the breathalyzer device. Improper calibration of the device makes the test unreliable. In order for the test results to be admissible in a court case, there are general guidelines that law enforcement must follow when it comes to their breathalyzer devices. The breathalyzer must be properly maintained and checked for accuracy at consistent intervals.

The person administering the breath test must be certified to use the device and administer the device in accordance with breathalyzer training. The officer administering the test must also ask the subject if they have burped, vomited, eaten, or smoked immediately prior to the breath testing. The breathalyzer must also be able to capture at least two measurements that are within .02% of each other in order for the results to be reliable.

In Connecticut, the law states that each person who gets behind the wheel and drives on the road has impliedly consented to a breath test that tests blood alcohol concentration. However, just as you may decline to take field sobriety tests and answer questions, you may also decline to take the breath test. The police legally cannot force you to take it.

But, there are consequences for refusing to take the test, such as automatic license suspension. However, the consequences of taking the breath test and having that evidence used against you in a criminal case may be far greater. A good attorney will be able to analyze a DUI case where there are breathalyzer results or a breathalyzer refusal and advise you on what defenses you may have. If you have been arrested for a DUI in Hartford, call Lady DUI to find out more.

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