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DWI BLOOD TESTS
Are blood tests more accurate than breath tests? Blood tests are not always reliable.

About David Breston
The Breston Law Firm has handled over 4,000 cases and has been helping people in Texas since 1987. Watch this video to find out more about our firm

CHOOSING A DWI LAWYER
Learn how to choose a DWI lawyer and the importance of choosing an experienced attorney.

DWI PENALTIES
A Texas DWI charge can cost you to lose your license, you face fines and may cost you your job.

DWI/DUI CHARGES
Have you been charged with Driving While Intoxicated (DWI)? Watch this video by David Breston explaining how he may be able to help you.

DWI BREATH TESTS
Should you refuse a breath test if you are pulled over for DWI in Texas? Watch this video to learn.

Houston Breathalyzer Tests Attorney

The first breathalyzer was manufactured nearly seventy years ago and today may be the most misunderstood tool in law enforcement’s arsenal to fight drunk driving. To begin with a breathalyzer is a machine that measures the amount of alcohol on your breath and not the actual amount of alcohol in your blood – to do that would require an analysis of a blood sample. This is just one of the misconceptions surrounding the machine that police have come to rely on when attempting to determine a driver’s level of intoxication.

Reliability of Breath Test Results in a Drunk-Driving Case

The most common tool used by law enforcement to determine a driver's blood alcohol content level is the breath test. However, it has lately been the subject of much controversy because it has been shown time and again to be an unreliable indicator of authentic blood-alcohol content level results. Let's first consider the definitions of some of the more pertinent related language.

BAC – blood alcohol content (also termed blood alcohol concentration). It is a metric of the level of intoxication used for medical or legal purposes and indicates the percentage of alcohol in an individual's blood. As an example, if you were to have a blood alcohol content reading of 0.10% then this would mean that 1/10 of 1% of your blood is actually alcohol.

Breathalyzer – a device for determining the blood alcohol content of an individual through a sample of his or her breath. Originally a brand name (think kleenex) it has morphed into a generic term for any machine that can perform this function. A breathalyzer is considered to be a scientific device. According to law enforcement, the advantage of its use is its non-invasive ability to gauge a level of intoxication versus medically withdrawing a blood sample with the use of a needle. Scientifically speaking, when a person drinks alcohol it is not digested but, rather, absorbed through the membranes in one's mouth and throat, stomach and intestines. From here it passes into the blood stream and leaves the body when a person exhales. The amount of alcohol in each exhalation is equal to the amount of alcohol in one's bloodstream. When a person breathes into a breathalyzer the air mixes with a chemical solution that causes a color change that is compared to a color chart for interpretation.

To the layman it may sound infallible but consider the following problems that have occurred.

  • The machine must be calibrated on a regular basis. This requires the intervention of an expert – not every police officer has this capability.
  • Breathalyzers are sensitive to light, heat and humidity. Think a police car on a hot summer night and you would agree that the 'room for error' with these instruments skyrockets.
  • Interpretation of the results is not always accurate – even when done by people who were 'trained' in the use and manipulation of breathalyzer devices and results.
  • Products other than alcohol can trigger the breathalyzer. For instance, mouthwashes all have some level of alcohol in them that could be picked up by the breathalyzer.

Most unsettling of all is the fact that police departments across the country have been found to admit to the unreliability of these machines In Virginia, an internal forensics document was uncovered that stated the current breathalyzers in use by law enforcement were 'unreliable and outdated'. In New Jersey, the judge himself threw out a DUI case after calling the breathalyzer results unreliable. Finally, there is evidence that police officers themselves have been found to tamper with the breathalyzer results.

Breathalyzer Accuracy

The State of Texas uses a machine called the Intoxilyzer 5000, which is commonly referred to as a "breathalyzer." Breath testing is predicated on Henry's law of physics, which states that if temperature, and pressure is held constant the substances in the corresponding gases and liquids will reach equilibrium and will be present in equal proportions. This means that the same concentration of a substance will be present in liquid and gaseous states. The problem is that if someone's temperature is above 98.6 they will probably have a higher breath test result.

  • The Intoxilyzer 5000 is supposed to measure how many grams of alcohol/ethanol per 210 liters of breath is in your breath. The sample chamber of the Intoxilyzer 5000 is 81 cubic centimeters or 81 cubic millimeters. If there is any error in the sample chamber it is magnified 2592 times.
  • The sample chamber is never cleaned and is replaced only about once a year. There creates a great possibility of contamination in the chamber. This contamination may affect the testing sample of someone who blows into the machine.
  • Researchers have found that substances such as Acetaldehyde, acetone, and Toulene may incorrectly read as ethanol during testing.
  • The machine is a self-testing machine. It is supposed to tell operators when there is a malfunction. The problem is that the operators and supervisors of the machine never perform any independent tests to see if the self-checking feature of the machine actually works.
  • The manufacturer does not warranty the Intoxilyzer 5000 for accurate and reliable breath testing.
  • The Intoxilyzer also assumes that everyone tested will have a blood/breath ration of 2100/1 (i.e. 2100 parts of alcohol in the breath for every 1 part of alcohol in the blood). If a person has a higher blood/breath ratio (i.e. 2400/1) the test will not be adversely affected by this assumption. However a person with a lower blood/breath ratio will be adversely affected because the Intoxilyzer will erroneously read too high, thus a person who should test at .05 or .06 could actually test well above a .08. Additionally, scientists have documented people with blood/breath ratios as low as 1100/1.
  • A person with a fever will have a higher breath test reading than an identical person without a fever. Therefore, the temperature of your body can affect what the Intoxilyzer reads, and your body temperature has nothing to do with the amount of alcohol you may have or have not consumed.
  • It has an acceptable rate of error of .02. This means that if the machine tested a subject and the test result came back .08 and then on a second test the result was .10 this would be within an acceptable margin of error for the machine. An everyday example is if you are stopped and arrested for DUI and take a breath test, and you blow a 0.080, when your actual alcohol content is something less, you still face the additional charge of driving with a .08 or higher. Very scary.
  • Another problem with the results of the Intoxilyzer 5000 is that it measures what your breath alcohol content is at the time of the test and not while you were driving. A person who has been drinking is either in the process of absorption or elimination. During absorption one's alcohol concentration is generally increasing. During elimination ones alcohol concentration is generally decreasing. Without knowing the time, manner, type and physical characteristics of the subject, there is an equal probability that the alcohol concentration prior to testing is higher, lower or the same as at testing.
  • The Intoxilyzer 5000 is based on very old technology. The brains of this outfit, a Z-80 microprocessor, which was introduced almost 30 years ago.

A lawyer experienced in drunk driving defense law is in the best position to advise a client on whether the Breathalyzer test results may be subject to challenge in his or her particular case. David A. Breston generally challenges Intoxilyzer 5000 results based on the following grounds:

  • The test operator must have a current certification.
  • The machine must have a current certification.
  • The machine must be calibrated as often as required.
  • The mouthpiece must be changed before the test is given.
  • There must be a record of the temperature of the calibrating solutions in the machine.
  • A log of the tests run must be kept.
  • The number of times the calibration solution has been changed must be counted.

Any of these details may show the inaccuracy of Intoxilyzer 5000 results, and Mr. Breston may be able to suppress this false evidence and get the charges against you dropped.

Often the results of a blood alcohol content reading become the cornerstone of the prosecution’s case against the alleged drunk driver. This is an important fact that cannot be overlooked when one is stopped and then arrested for suspicion of driving while intoxicated. Due to the fact that the machine and potential results are riddled with problems it is most likely a better choice to refuse law enforcement’s request for a breathalyzer test and request a Houston DWI attorney instead.

When your future is at stake, it is important that you enlist the
assistance of a DWI defense lawyer who not only understands
your situation but also has a thorough knowledge of the drunk
driving (DWI) laws and procedure in Texas. Mr. Breston
devotes himself to examining all aspects of your case in
order to construct the strongest possible defense on your
behalf. Let him conduct an investigation and determine the
best way in which to pursue a resolution to your situation.

as soon as possible for a free consultation.
He can help you fight for your rights.