In the court of law, breathalyzers and blood tests form the scientific backbone of many DUI investigations. Law enforcement relies on the accuracy of these tests to determine how much alcohol a driver may have consumed and secure DUI convictions. However, the science behind breathalyzer and chemical tests in DUI cases can present complexities.
Understanding the intricate science and processes at play is crucial. When knowledgeable Los Angeles DUI attorneys scrutinize the scientific details, we can often uncover issues that create doubt about chemical test validity. In this article, learn how DUI tests work, what factors weaken the prosecution’s evidence, and other DUI strategies that can be used to challenge a DUI test.
What is the Scientific Reasoning Behind a Breathalyzer Test?
According to Healthline, breathalyzer tests are based on the scientific principle of alcohol metabolism and the correlation between the concentration of alcohol in a person’s breath and blood alcohol concentration (BAC). The scientific reasoning behind a breathalyzer and chemical test for driving under the influence involves several key scientific factors:
Alcohol Absorption and Elimination
When alcohol is consumed, it is rapidly absorbed into the bloodstream through the walls of the stomach and small intestine. From there, it is distributed throughout the body, including the lungs, where it can be detected in exhaled breath.
The rate at which alcohol is absorbed and eliminated from the body is influenced by various factors, such as the person’s weight, metabolism, and the presence of food in the stomach.
Partition Ratio
The partition ratio refers to the relationship between the concentration of alcohol in a person’s breath and their BAC. This ratio is relatively constant across individuals, with an average value of approximately 2,100:1. This means that for every unit of alcohol in the blood, there will be about 2,100 units of alcohol in the breath.
Infrared Spectroscopy or Fuel Cell Technology
Breathalyzer devices utilize either infrared spectroscopy or fuel cell technology to measure the alcohol concentration in a person’s breath. Infrared spectroscopy involves passing infrared light through a breath sample and measuring the absorption of specific wavelengths of light by alcohol molecules.
Fuel cell technology utilizes a chemical reaction that occurs when alcohol comes into contact with a fuel cell, generating an electrical current that is proportional to the alcohol concentration.
Calibration and Standardization
Breathalyzer devices require regular calibration using a known alcohol reference solution to ensure accurate and reliable results. Calibration adjusts the device to provide accurate readings based on known alcohol concentrations. Additionally, breathalyzer devices are typically standardized to a specific partition ratio to account for individual variations and enhance the accuracy of the results.
It’s important to note that breathalyzer tests provide an indirect estimation of a person’s BAC, as they measure the alcohol concentration in the breath rather than directly in the blood. While breathalyzer tests are widely used and generally considered reliable, they are not infallible, and there can be factors that affect the accuracy of the results.
What Variables Can Distort a Breathalyzer Test?
Variables like calibration, storage, collection methods, and physiologic factors of the driver can distort BAC readings and test results. While breathalyzer tests are generally considered reliable, the following factors can affect the accuracy of the results:
- Mouth alcohol: Mouth alcohol can be caused by recent alcohol consumption, the use of mouthwash or breath fresheners containing alcohol, or regurgitation. It can artificially inflate the alcohol concentration in the breath sample, leading to higher readings than the actual BAC.
- Interfering substances: Certain substances, such as volatile organic compounds (VOCs) found in some paints, solvents, and cleaning agents, can potentially interfere with breathalyzer results. These substances may be mistakenly detected as alcohol by the breathalyzer device, resulting in false positive readings.
- Residual alcohol: Residual alcohol in the oral cavity can also affect breathalyzer results. If a person has recently consumed an alcoholic beverage, traces of alcohol can remain in the mouth, even after sufficient time has passed for alcohol to be eliminated from the bloodstream. This can artificially elevate breathalyzer readings.
- Breath temperature: Breathalyzer devices are typically calibrated to assume a specific temperature range for the breath sample. Variations in breath temperature, such as extremely hot or cold breath, can potentially affect the accuracy of the results. Some breathalyzer models have temperature sensors to compensate for this factor.
- Device calibration and maintenance: Improper calibration or maintenance of the breathalyzer device can introduce inaccuracies in the results. Regular calibration using a known alcohol reference solution is necessary to ensure that the device provides accurate readings. Neglecting maintenance can compromise the reliability of the device.
- User error: Errors in conducting the breathalyzer test can also impact the accuracy of the results. Improper administration, failure to observe the required waiting period, or inadequate operator training can introduce errors that affect the reliability of the readings.
Knowing how your Los Angeles DUI attorney can leverage science and expose flaws in the state’s evidence could impact your criminal case outcome for the better.
Is There a Chemical Process Used to Test for Drunk Driving?
Breathalyzers and chemical tests in DUI cases scientifically measure blood alcohol levels indirectly by analyzing the amount of alcohol present in a person’s breath. The process involves several steps and relies on specific biological and chemical factors.
Biological Factors
When alcohol is consumed, it is absorbed into the bloodstream through the digestive system. As blood circulates through the body, a portion of the alcohol is carried to the lungs, where it diffuses into the air sacs. When a person exhales, the alcohol molecules present in their breath can be measured.
Chemistry Inside Devices
Breathalyzers use a technology called infrared spectroscopy or fuel cell technology to detect alcohol levels in the breath. Infrared spectroscopy measures the absorption of infrared light by alcohol molecules, while fuel cell technology uses a chemical reaction to produce an electrical current when alcohol interacts with the fuel cell.
How Do Errors Occur in Blood Testing for DUIs?
The science regarding breathalyzers and chemical tests for DUIs can be subject to errors in the following ways:
Contaminated Blood Vials
Blood vials used for collecting and storing blood samples must be properly cleaned and free from contaminants. Contamination of the vials can introduce substances that may interfere with the analysis and potentially skew the BAC data.
Delays in Processing
Timely processing of blood samples is crucial to maintain the integrity of the results. Delays in transporting, storing, or analyzing the blood samples can lead to changes in alcohol concentration over time, potentially resulting in inaccurate BAC readings.
Following Medical Standards
Proper blood draw procedures should adhere to recognized medical standards. Failure to follow these standards, such as improper sterilization or incorrect storage conditions, can compromise the accuracy of the blood test results.
What Defenses Could Be Used to Question a BAC Reading in a DUI Case?
Several physical factors can influence blood alcohol concentration (BAC) readings and should be taken into account during testing. Such as
- Time Since Drink: BAC readings can be influenced by the time elapsed since the consumption of alcohol. It takes time for alcohol to be absorbed into the bloodstream, so BAC levels may continue to rise even after the person has stopped drinking. In cases where testing occurs close to the time of consumption, BAC readings may not accurately reflect the person’s impairment level.
- Health Issues: Some health conditions, such as diabetes or certain metabolic disorders, can affect the body’s processing of alcohol. These conditions may alter the rate at which alcohol is metabolized, potentially leading to higher or lower BAC readings compared to individuals without these conditions.
- Medications: Certain medications can interact with alcohol and affect BAC readings. For example, medications that contain alcohol or those that affect liver function can interfere with the body’s ability to metabolize alcohol, leading to higher BAC readings.
What Can Be Done if the Breathalyzer and Chemical Test for a DUI is False?
If you believe that the science behind a breathalyzer or chemical test for a DUI is false or inaccurate, a successful DUI lawyer in Los Angeles can carefully examine the testing procedures to identify any errors that may have occurred, including reviewing documentation, observing the administration of the tests, and investigating potential deviations from standard protocols.
We can also assess maintenance records to identify weaknesses in the prosecution’s case and raise reasonable doubts about the accuracy and validity of the test results. It is a DWI attorney’s role to challenge the test’s accuracy, chain of custody, and admissibility. Contact us today to assess your situation and bolster a defense argument.
