What is a DUI-DWI Breathalyzer and how does it work?

Although regularly referred to as a DUI, in North Carolina, driving under the influence is defined as a DWI-driving while intoxicated. A breathalyzer is a device used to estimate blood alcohol content (BAC) from a sample of an individuals breath in order to establish evidence for a charge of DWI-driving while intoxicated. Although a generic name today, the original “Breathalyzer” was a brand name of a series of models designed to produce evidence for DWI’s that were manufactured by Smith and Wesson . Today, the most common brand names are the Intoxilyzer, Intoximeter, AlcoScan, Alcotest, AlcoSensor, Alcolizer, and Datamaster. The NHTSA (National Highway Traffic Safety and Administration) governs the Conforming Products List of breathylzers that are approved for evidentiary and preliminary screening use for DUI-DWI testing.

Analyzers do not measure actual blood alcohol concentration, which requires a blood sample. They only estimate BAC by indirectly measuring the alcohol from an individuals breath. A Charlotte DWI Lawyer should know that within testing, there are two common types of technology that are generally used: a Desktop tester that utilizes infrared spectrophometer technology, and electrochemical fuel cell technology. Hand held field sobriety devices are generally based on electrochemical fuel cell, and are used in field sobriety testing known as PBT (preliminary breath test), PAS (preliminary alcohol screening), or POA (point of arrest) testing.

Once an individual has blown into a device, a district attorney or commonwealth attorney may use this as evidence towards a defendant’s guilt for blowing a BAC of .08% or higher. Even though blowing a BAC of .08% or higher isn’t necessary to be convicted of a DWI, the breathalyzer reading will then be offered into evidence. Certain devices are admissible in court, while others are not. The SD-2 and the Alcosensor III are know as PBT’s (Preliminary Breath Tests) and are generally not admissilbe in court for the prosecution of a DWI, even though they are used to establish probable cause for an arrest. The Intoxilyzer 5000 is an example of a Evidentiary Breath Testing Device (EBT) used in Mecklenburg-North Carolina and surrounding counties, and is admissible in court as evidence toward a person’s intoxication for a DWI in Charlotte-Mecklenburg County.

Eventhough a breathalyzer’s reading may be admissible into court, a Charlotte DUI lawyer may be able to defend these readings by finding a common source of error. Competent Charlotte DWI lawyers know that breathalyzers can be very sensitive to certain variables such as outside temperature and a subjects temperature. If you choose the right Charlotte DWI Attorney, it should also be common knowledge that breathing patterns can also significantly affect test results. A common source of error that may occur happens when NC Law Enforcement or breathalyzer administrators fail to recalibrate in accordance to strict guidelines that governs officer training, instrument maintenance, and instrument calibration. Due to this, certain DWI-DUI agencies around the world such as the police in Victoria Australia factor in a 20% tolerance on readings.

Calibration differs in the type of device that is used for Mecklenburg County DWI’s. Most handheld devices use silicon oxides sensors to determine BAC. This requires proper software to calibrate the accuracy of the sensors, which deteriorate over time. However, as technology has advanced, many new models have self calibrating devices or sensors that are easily replaced to avoid calibration to take place in a North Carolina DWI lab.

A major problem with some older machines are that they identify ethenol known as ethyl alcohol that is found in liquor or alcoholic beverages as well as other substances that have a similar molecular structure. Some of these models pass a person being tested for a DUI-DWI through a solution of potassium dichromate that oxidizes the ethenol into a substance known as acetic acid that changes the color during the process. This color change is used to determine a persons BAC reading. A problem that can occur is due to potassium dichromate being a strong oxidizer that can cause numerous alcohol groups to oxidize by producing false positives for a result which is then applied as DWI evidence in North Carolina.

Competent Charlotte DWI Lawyers also know that other problems may arise from interfering compounds. The NHTSA (National Highway and Traffic Safety Association) has found that individuals that diet and are diabetic can have acetone levels that are hundreds and even a thousand times higher than found in an average person. Acetone is an example of a substance that has been found to be falsely identified as ethenol by some breathalyzers when testing for a DWI-DUI; however, most new machines now use filters that separate substances such as acetone.

An experienced Charlotte DUI Attorney knows that Homeostatice Variables are another factor that may cause a false reading due to breath machines assuming that individuals have a 2100 to 1 partition ratio when alcohol is converted in the breath to estimate alcohol in someones blood. By assuming that every individual has a 2100 to 1 partition ratio, a beathaylzer does not take into account that partition ratios can vary from 1300 to 1 all the way to 3100 to 1. If this is found it be true for an indiviual being tested for a DWI in Charlotte North Carolina by a police officer, an individual with a BAC of .07% and a partition ratio of 1500 to one may actually blow a reading of .10% which is above the legal limit of .08% by .02%. With this in mind, most individuals do have a 2100 to 1 partion ratio that was found in William Henry’s Law in 1803. Yet, certain studies have shown that up to 1.8% of the population may have a partition rate below 2100.

Probably the most common cause of producing a false reading is mouth alcohol. Machines that test for DUI and DWI’s assume that when someone is blowing, alcohol is coming from alveolar air, which comes deep from a persons lungs. However, alcohol may register in a device from the mouth, throat, or stomach. This is why certified DUI-DWI breathalyzer operators usually observe an individual for 15 minutes or more before administering a test in order to charge someone with driving under the influence.

Mouth alcohol can cause problems because it is not absorbed through the bodies stomach and intestine, which passes through the blood to the lungs. Due to this, a very small amount of alcohol in someone’s mouth, throat, or stomach may cause a much higher than normal reading.

Recent drinking, belching, burping and acid reflex are the main source of mouth alcohol. This is found when alcohol in the form of a liquid or gas rises up to the tissue in the esophagus or oral cavity. Dentures and individuals with Periodental disease can also trap alcohol in the mouth causing a false reading in a breathalyzer leading to a Driving While Intoxicated in Charlotte, North Carolina.

As discussed above, testing an individual too early for a DUI or DWI, while their body is absorbing alcohol may cause an inaccurate reading due to alcohol absorption lasting from 45 minutes to 2 hours. In the absorbtive phase, alcohol is not proportionaly distributed throughout the body, causing certain parts of the body to have a higher BAC than others.

Once an individual has blown, as noted above, this reading will be introduced into evidence during a trial for driving under the influence. To assist the district attorney in Charlotte DUI prosecution, evidence of Retrograde Extrapolation may be introduced. A Charlotte DWI Lawyer is normally required to explain this process, which attempts to provide the BAC back in time while an individual was driving by applying mathematical formulas known as the Widmark factor. Although this factor is highly criticized, it is just another reason why hiring a competent DUI-DWI Lawyer in Mecklenburg County North Carlina is necessary to your defense.

Contact the Law Offices of David Sheehan and speak with a Charlotte Mecklenburg County DUI-DWI Lawyer today.

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