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Portable Evidential Breath Test (PEBT)

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Driving in the State of California is a “conditional privilege.” This means that properly licensed persons may operate motor vehicles in the State of California, but there are strings attached. One of the strongest requirements placed upon a driver is that if lawfully arrested for DUI, he or she must submit to a chemical test of their blood or breath to determine the blood/alcohol concentration in their body.

For a chemical blood or breath test to be “presumed” accurate, it must be completed within three hours of the termination of driving.

This is because as time passes, the human body will absorb and then eliminate the alcohol accumulated in the bloodstream. Because of this, law enforcement officers are trained to collect the evidentiary blood or breath samples as quickly as possible following the arrest.

For decades, this has required law enforcement officers to transport the arrested driver from the scene of the stop to a police station, jail, or hospital to administer the blood or breath test. In years past, the breath machines in the station were large, bench-mounted, devices that resembled computers.   The process of transporting prisoners and then setting up the large breath devices invariably caused delays in collecting the evidentiary samples. This can result in the breath samples that do not accurately reflect the blood/alcohol concentration at the time of driving.

In an effort to minimize this passage of time, many California law enforcement agencies have begun using evidentiary breath devices that are administered right at the side of the road. The Portable Evidentiary Breath Test device, also known as a “PEBT” is a small “hand-held” breathalyzer, very similar to the Preliminary Alcohol Screening (PAS) devices that have been used in the field by police officers for years. In fact, some of today’s hand-held devices known as Evidential Preliminary Alcohol Screening (EPAS) devices perform the dual functions of a “Screening Device” and an “Evidentiary Device.” By simply flipping a switch, the arresting officer can change the device from screening mode into evidentiary mode. The theory is that breath samples that are taken shortly after the time of driving are going to more accurately represent the driver’s true blood/alcohol concentration than a sample that may be taken later at a different location.

How Does a Portable Evidential Breath Test (PEBT) Work?

If a driver in California is lawfully arrested for DUI, he or she is then mandated by law to provide an official “evidential” sample of their blood or breath to determine their blood/alcohol concentration. If the affected driver chooses to provide a breath sample, the arresting officer has the option to use a Portable Evidential Breath Test (PEBT) or Evidential Preliminary Alcohol Screening (EPAS) device right at the scene to collect the air samples. The driver has no right to demand that the air samples be taken at a police station or a hospital. If the driver has elected to provide an breath sample to determine his or her blood/alcohol concentration; and if the arresting officer is equipped with a PEBT or EPAS device, the driver must blow into the device of face the possibility of being accused of a Chemical Test Refusal.

The technology available in the PEBT is similar to that available in the larger “bench-mounted” devices at police stations. Also, for PEBT breath samples to be used as evidence at a DMV Administrative Per Se Hearing, they must be collected in substantial compliance with the rules established in Title 17 of the California Code of Regulations. Title 17 is a series of procedural regulations controlling the collection of blood, breath or urine samples that are then used in criminal and administrative proceedings to establish a driver’s blood/alcohol concentration. If a law enforcement officer fails to follow the standards established in Title 17, it could potentially result in the breath samples being corrupted or otherwise rendered inaccurate.

The most important standards established by Title 17 for the use of PEBT devices are:

  • The PEBT device must be regularly maintained and it must be checked for accuracy every 10 days or 150 tests;
  • The law enforcement officer administering the PEBT test must be trained and certified in the use of the particular device;
  • The law enforcement officer administering the PEBT test must continuously observe the test subject for 15 minutes prior to the breath sampling to ensure the subject does not eat or drink anything. The subject must not smoke and must not burp, regurgitate or vomit, as any of these events can cause a falsely high reading on the PEBT.
  • The law enforcement officer administering the PEBT must collect two samples of “deep lung air” with readings that are within .02% of each other. If there is too great a difference in the two readings, the officer may compel an additional sample.

There are other procedural steps that should be taken. For example, the administering law enforcement officer should ensure that the PEBT’s batteries are fully charged, that the LED screen is functioning properly, and that there is no Radio Frequency Interference (RFI).

Once the test subject has provided adequate samples, the law enforcement officer should place the device back in the cradle of its carrying case. This causes the PEBT device to download its information into a hard drive which then prints a small receipt of the test results. This breath test strip is often attached to police arrest reports to establish the blood/alcohol concentration as measured by the PEBT device.

Are Portable Evidential Breath Test (PEBT) Devices Accurate?

When field breath analysis first came into existence, the devices were little more than straws or balloons that would turn a certain color if they detected the presence of alcohol on a driver’s breath. Today’s devices have become wonders of Fuel Cell Technology. However even the finest PEBT devices today are still machines, and machines are subject to corruption, malfunction and inaccuracy.

PEBT devices work by detecting methyl based chemicals on the human breath that absorb infrared light. When the PEBT device detects the presence of such a chemical, it assumes it is alcohol and then conducts a mathematical computation to convert the amount of chemical present on the breath to a quantitative estimate of the alcohol present in the person’s blood stream.

Specificity: PEBT devices presume that any compound introduced into its air chamber which absorbs infrared light, must be Ethyl Alcohol (the active compound in alcoholic beverages). The reality is that many methyl based chemicals absorb infrared light the same way Ethyl Alcohol does and so any methyl based chemical introduced into a PEBT devices is going to be presumed to be Ethyl Alcohol.

There are many methyl based chemicals that occur on the human breath. For example a person who is on a high-protein, low-carbohydrate diet may have elevated levels of ketone on their breath. A person with diabetes may have an elevated level of acetone on their breath. Although perfectly legal and non-impairing, these two methyl based chemicals will be identified as Ethyl Alcohol by a PEBT. The lack of specificity is a real problem in PEBT testing.

Partition Ratios: Once a PEBT device detects the presence of “alcohol” on the subject’s breath, it must mathematically extrapolate that number into something that estimates the blood/alcohol concentration.

To make this computation, PEBT devices use a “partition ratio” of 2,100 to 1. This means that PEBT devices detect the presence of a methyl based chemical on the breath, assume it to be alcohol, and then determines the amount of “alcohol” present in 2,100 milliliters of breath is equivalent to the amount of “alcohol” in 1 milliliter of blood.

This science is terribly flawed as it presumes that every single person in California will have a partition ratio of 2,100 to 1. Regardless of age, sex, or body weight, the PEBT devices will always use the 2,100 to 1 ratio when computing blood/alcohol concentrations. This is just bad science.

Calibration, Maintenance or Accuracy Problems: As stated above, machines are machines. They are subject to malfunctions and other mechanical or technological failures. The PEBT device must be maintained by a certified forensic laboratory and accuracy checks must be conducted by testing the device with solutions or powders that contain a known alcohol content. Failure to maintain or calibrate these devices can result in inaccurate readings.

 Operator Error: If the administering law enforcement officer does not properly attach the mouthpiece to the PEBT device or if he fails to change the mouthpiece between consecutive blows, this can cause inaccurate readings. If he officer fails to clear the subjects mouth of gum, mints or chewing tobacco; this can have an adverse effect on the accuracy of a PEBT device.

 Medical/Dental Issues: As stated above, today’s PEBT devices lack specificity and will often identify any methyl based chemical on the breath as alcohol. If a person is on a high-protein diet, the human body burns fat. The by-product of this process is Ketone. Ketone is a methyl based chemical that is dispersed through the breath and exhaled air. A person who suffers with diabetes or hypoglycemia may have elevated levels of Acetone on the breath. All of the compounds will be identified as alcohol when introduced into to the PEBT’s air chamber.

If a person has significant dental work (i.e. Bridges, Braces, Retainers) in their mouth or if they have a pierced tongue; these are all locations where alcohol may pool and can cause abnormally high readings when blowing into a PEBT device.

The presence of “mouth alcohol” can cause a PEBT device to read residual alcohol in the mouth as opposed to what is truly present in the blood stream. Even though you may not be impaired, the device can detect the residual alcohol in your mouth, multiply it 2,100 times and determine you are above the legal limit. This is not perfect science.

Call CDA Today. We’re Ready to Help You Attack the PEBT Reading.

The DMV Defense Experts at California Drivers Advocates include former law enforcement officers who have worked with all varieties of PAS, EPAS and PEBT devices. We know where mistakes are made and we know what can make these devices fail. When it comes to attacking the accuracy of a Portable Evidential Breath Device, nothing beats experience and training.

Call CDA today. We can completely investigate the PEBT device used in your case. We can examine its maintenance and accuracy records, we can examine how it was administered and we can determine if you have any medical, physical or dental issues that could corrupt the samples.

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