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Roadside Breath Test

California DUI arrests often stem from roadside breath tests, which measure a driver's blood alcohol content (BAC). Although prosecutors often use roadside breath test results as the centerpiece of a drunk driving case, in truth these tests aren't always accurate, and can often be successfully challenged in court. An experienced California criminal defense attorney who focuses on DUI cases knows how to challenge PAS tests roadside breath test results in a drunk driving case.

Two types of roadside breath tests are given in California Driving Under the Influence (DUI) investigations: Preliminary Alcohol Screenings (PAS) or Preliminary Breath Test (PBT) tests, which are merely screening tests given to provide probable cause to make an arrest, and roadside evidential tests. There are important distinctions between the two.

Preliminary Alcohol Screenings tests, or PAS, are voluntary tests not covered by California's implied consent law. In fact, in many states, the officer performing the roadside DUI investigation is required to advise the driver that he or she has the option of refusing the test, but if an arrest is made, the driver will then be required to submit to a test of his or her blood or breath to determine alcohol content.

Unfortunately, some officers ignore this responsibility when conducting a driving under the influence (DUI) roadside investigation. Motorists have reported that officers thrust collection tubes into drivers' mouths without giving them a chance to refuse. A drunk driving arrest invariably follows. It likely would have followed anyway, except now the unwitting motorist has provided additional evidence for the government to use in a DUI prosecution.

Roadside breath testing has been around for years. In the early days, it was readily acknowledged that the technology used in roadside testing was somewhat inferior, and PAS tests were not reliable enough to be admitted into evidence. Therefore, when police used an alcohol screening test as part of a DUI investigation, the only thing that could be introduced in evidence at a California DUI trial was that the PAS test indicated the presence of alcohol - the numeric results were excluded.

Regrettably, that is no longer true. In recent years, courts have allowed the numeric results of PAS tests to be considered by juries, so long as certain evidentiary foundations were established. As a result, motorists targeted for drunk driving roadside investigations are taking voluntary roadside breath tests, only to have the numeric results introduced at trial. An experienced California criminal defense lawyer who specializes in DUI cases knows how to challenge PAS tests in a drunk driving case.

In California roadside DUI investigations have become even more complicated by the recent addition of the Evidential PAS test, also known as the "E-PAS" or AlcoSensor IV XL. These are the roadside breath test that is required under the implied consent laws. The mandatory test is given on the exact same machine that was, moments earlier before the driver was arrested, an optional test. The only difference is that now, in a post-arrest setting, they are able to print out the results, unlike a screening test, which merely displays the results on an LED readout.

The motorist sometimes doesn't even realize the moment that he or she was placed under arrest for drinking and driving. One minute a driver is offered a roadside test, and told it is optional. The next, the motorist is informed that a roadside breath alcohol test on the same machine is mandatory. It is obvious how confusion can result. This is why many California DUI defense lawyers advise people to refuse all roadside breath tests and insist upon a blood test if they are ever the target of a drunk driving investigation.

Once the driver is arrested, the "implied consent" law comes into play. Implied consent means that by accepting a driver's license, every motorist has consented to a test of blood or breath to determine alcohol content following a DUI arrest. The failure to give this blood or breath sample following a drunk driving arrest can result in administrative sanctions from the California Department of Motor Vehicles (DMV) resulting in a minimum one-year driver's license suspension, with no opportunity for a restricted or provisional license during that year.

Roadside breath testing was developed to address a significant issue in DUI prosecutions - because so much time typically elapses between driving and testing, there was often an issue of whether the motorist's alcohol level could have been below the legal limit at the time of driving, and then rose to a level that exceeded the legal limit at the time of testing. The aim of roadside breath testing in DUI cases was to eliminate that issue by fixing the blood or breath alcohol level (BAC) nearer the time that the driver was behind the wheel.

While the goal of achieving greater scientific certainty is laudable, in practice, there are significant problems that eclipse any advances made. The challenges to both the PAS test (the pre-arrest roadside breath test in California DUI investigations) and the E-PAS (the post-arrest roadside breath test) are the same.

DUI prosecutions are just like any other criminal case. Prosecutors must prove each element of the case beyond a reasonable doubt, to the exclusion of every reasonable doubt, in order to get a conviction. If the prosecutor is unable to present a case that is 100 percent free of reasonable doubt, the jury must acquit. This notion is at the heart of every criminal case, whether it is driving under the influence of alcohol, DUI drugs, vehicular manslaughter, robbery, assault, or murder.

The first challenge against breath testing machines relates to their accuracy, calibration, and maintenance. Both field breath testing units and stationhouse breath testing units are delicate instruments that can become inaccurate, and it is vital to explore these issues in every drunk driving prosecution.

It is just as important to determine whether the officer who administered the test was properly trained. Only those who have gone through appropriate training should be performing these tests on motorists suspected of driving under the influence of alcohol.

An effective challenge to roadside breath tests in a California DUI arrests relates to the technology of the machine itself. The roadside PAS devices are "fuel cell" machines. In short, alcohol is oxidized on an electromagnetic plate, and the amount of electrochemical energy generated is converted to a number that is supposed to be equal to the blood-alcohol level of the motorist.

This technology invites numerous problems, including the possibility that other compounds in the human breath are misinterpreted as alcohol, buildup that creates falsely high results, and, most importantly, the lack of a mouth alcohol detector.

Mouth alcohol is one of the most prominent issues in forensic breath testing. The danger of mouth alcohol contamination drives many of the rules and regulations in breath testing, such as the15- or 20-minute waiting period, the need to observe the subject to ensure there is no regurgitation or introduction of foreign material in the mouth, and the requirement of obtaining two samples that agree with one another. These are all critical issues in a California DUI cases, and especially in cases involving the PAS machine. An experienced California DUI defense lawyer know how to challenge PAS tests roadside breath test results in a drunk driving case.

This is important because the PAS machine does NOT have a mouth alcohol detector, also called a slope detector. Mouth alcohol detectors are computer software programs that are designed to detect a rapid drop-off - or slope - in the alcohol level of an individual breath sample. The machine is not smart enough to know whether it is analyzing alcohol molecules in the deep lung air - what it is supposed to be measuring - or alcohol molecules that have been trapped in the mouth or regurgitated from the stomach. This is especially problematic when a driver is given a breath test shortly after drinking, while alcohol is still in the stomach, or has been trapped in the mouth due to dental work or food traps.

Another problem with PAS testing is that it does not measure breath temperature. The machine's calculations are based on the assumption that the subject's breath temperature is 34 degrees centigrade. Unfortunately, just like every other assumption that is made about the "average" person, any variation from "average" can greatly impact the reading. Every degree of temperature elevation - which could be from illness, dancing, or engaging in sports activities - equals a 7 percent increase in alcohol percentage.

Many drivers who are targeted for DUI investigations are simply poor candidates for breath testing. Criminal defense lawyers know that those who have had recent dental work, or who suffer from GERD (gastro esophageal reflux disorder, the technical name for persistent heartburn) are inappropriate subjects for breath testing. There are many other conditions that could cause an unnaturally high reading on a breath test.

Because so many variations exist that affect the accuracy of roadside breath testing, the results can be effectively challenged. It is therefore vital for anyone arrested on DUI charges to contact a California DUI defense attorney who understands these issues. The results of the roadside breath test are often the most damning evidence offered in a drunk driving case. It is essential that these results be challenged to achieve a successful result.

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