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Protecting Your Rights


“Do I Have a Chance?”

Why Drivers Should Never Assume They Will Be Found Guilty.

If nothing else, this website should give you a sense of the complexity of a DUI charge in Virginia. They are complicated to defend, and, more importantly, they are complex crimes to prosecute. DUIs are never as simple as they look, and a driver is always innocent until proven guilty.

In order to successfully prosecute DUIs, prosecutors, police, breath technicians, and the Virginia Department of Forensic Science personnel must all comply with strict and complex laws. There are dozens of ways that any one of these people can make a mistake that could affect the outcome of a DUI case. Even if a mistake does not result in an acquittal, it may result in a lesser sentence.

The following sections lay out just a few of the many issues that may affect the outcome of your DUI trial.

Jurisdictional Issues


Where a crime occurs dictates which courts can hear a case and which officers can arrest a driver. For example a George Mason University police officer may not be able to stop and arrest a driver for DUI outside the boundaries of George Mason University and its abutting roads. Also, the Prince William County General District Court may not hear a DUI case if the intoxicated driving did not occur within Prince William County.

Warrantless Arrests


For most DUI cases in Virginia, if an officer arrests a person for DUI but did not personally witness them driving, then he must prove that the arrest occurred at the scene of an accident, at a hospital (after an accident) or somewhere else if the DUI occurred within 3 hours of the arrest. If an officer cannot meet this burden then the court may dismiss the DUI case entirely.

Unconstitutional Traffic Stop


For most situations, in order to pull a driver over, an officer must have a “reasonable articulable suspicion” that crime is occurring.

If an officer cannot articulate why they reasonably suspected that the driver had broken the law prior to being pulled over then the court may declare the traffic stop unconstitutional and dismiss the DUI.

Vague accusations such as “he looked like he was speeding” or “he was driving funny” may not be enough to justify a traffic stop.  If a judge finds that the stop was unconstitutional then the DUI may be dismissed.

Unconstitutional Arrest


In order to arrest a person for DUI a law enforcement officer must have “probable cause” that the driver was intoxicated before the arrest. Without probable cause, the arrest is usually invalid and the DUI case may be dismissed. The court may also dismiss a refusal charge as well.

When an attorney challenges the constitutionality of a DUI arrest in Virginia the attorney is usually attacking at least one of four types of evidence in the following order: 1) The PBT result, 2) The Field Sobriety Test results, 3) the driving behavior, and 4) Other signs of intoxication (odor, slurred speech, blood shot eyes, lack of coordination, etc.).

Intoxicated At the Time of the Offense (Rising BAC)


In Virginia, the government must prove that a driver was drunk at the time they were operating the vehicle not just when tested at the station. If your PBT results at the scene were much lower than your ETD blood alcohol levels at the station you may be able to prove that you were not legally intoxicated at the time you were pulled over. This defense is particularly relevant when a person drank alcohol immediately before being pulled over. In that situation the alcohol in their stomach had not yet entered their blood stream at the time they were driving. Consequently, it may be argued that the driver would have arrived home before becoming legally intoxicated had they not been arrested.

Operating a Vehicle


If the police officer who arrested you did not personally witness you operating your vehicle there may be a good legal defense to your DUI. This situation is most common where the police respond to an accident or where the police find the driver sitting or sleeping in their car. Even if the officer can prove that a driver drove to the spot where he was found, it does not mean that the person was intoxicated at that time.

Field Sobriety Tests


Field Sobriety Tests are completely voluntary. In Virginia, an officer is never allowed to force a driver to take an FST. If an officer orders, forces, or requires a driver to take an FST then the court may find that the FST violated the driver’s fourth amendment rights. The courts may then order all evidence related to the FST to be excluded from the trial.

The Nine Step Walk and Turn & The One Leg Stand


These field sobriety tests must be performed in an appropriate location. The ground must be flat, level, hard, non-slippery, clear of any debris, reasonably quiet, safe from traffic and other potential distractions or safety issues. Extreme weather can also effect the accuracy of this test.

Like other tests, these tests check a driver’s ability to follow instructions. Any language barriers, deafness, excessive noise, learning disabilities, mental retardation, developmental issues, etc. can possibility skew the outcome of these tests.

If a driver has any problems balancing, walking, or standing then these tests may not be valid. Being over the age of 65, obesity (more than 50 pounds overweight), injuries to your back, legs, feet, knees, etc., inner ear problems, vertigo, clubbed feet, and arthritis are all examples of medical conditions that could affect the accuracy of these tests.

An officer should asked detailed questions about a driver’s medical and physical condition prior to administering these field sobriety tests in order to guarantee that these conditions are not present. Any time a driver is asked to perform either of these field sobriety tests after being in a serious accident, the results of this test should be questionable.

Horizontal Gauze Nystagmus Test (HGN)


This test must be administered very precisely in order to be an accurate gauge of intoxication. If an officer moves the stimulus (their finger or a pen) too quickly (i.e. faster than two seconds per pass per eye) it may cause uneven tracking. Holding the stimulus more than slightly above the eye line may also induce nystagmus. Making the driver hold their eyes at maximum deviation for too long or too many times can also lead to fatigue-induced nystagmus. Testing a driver while cars or other fast-moving objects are within the driver’s field of vision can also induce nystagmus.

Medical conditions, including injury from a car accident can cause nystagmus. An officer should check for resting nystagmus and for equal pupil size prior to beginning the test to guard against these types of false positives.

The Alphabet Test


This test should never involve reciting the alphabet backwards. Additionally, this test is less reliable when the driver is not a native English speaker. An officer should ask a driver about their ability to understand and speak English if they are not a native speaker. Testing in an extremely noisy environment can also cause the officer to hear errors that are not really present. Speech impediments, injuries to the lips or mouth, and an assortment of mental conditions can cause a false positive.

Finger Dexterity Test


As with other field sobriety tests, medical conditions, injuries, shock, language barriers, or any other condition that affects hand coordination or a driver’s ability to follow instruction may invalidate this test.

Private Property


In Virginia, if a driver is arrested for DUI on a private road, parking lot, or driveway the government may be prevented from using or mentioning the breathalyzer results at trial. The legal issues surrounding arrests on private property are extremely complicated so talk to a local DUI attorney in detail if you believe that you were arrested for DUI on private property.

Preliminary Breath Tests (PBTs)


In order to arrest a driver for DUI in Virginia, an officer must have enough evidence to show “probable cause” to a magistrate or judge. Preliminary Breath Tests (PBTs) cannot be used as evidence of intoxication for a conviction; however, a PBT can be used to justify an arrest. If a driver wants to invalidate an arrest for DUI, attacking the PBT may be essential.

In Virginia, in order to use a PBT to justify an arrest, the police must do four things: 1) they must use an approved brand and model of PBT; 2) they must use and maintain the PBT according to the manufacturer’s instructions; 3) the PBT must be properly calibrated; and 4) the officer must inform the driver of his right to see the results of the PBT.

The law requires that the PBT be used according to the manufacturer’s instructions, but, unfortunately, such use is not common practice. For example, the Alco-sensor III must not be used if the machine’s temperature is below 59°F (15°C) or above 96°F (36°C). However, most officers keep their PBT in the trunk of their patrol car where it is either very cold or very hot.

Also, many PBTs are vulnerable to radio frequency interference (RFI) or radio signals from police officers’ communication devices. Radio signals can strike the PBT’s extremely sensitive voltammeter and cause sporadic readings. If the digital read-out flickers, the screen blanks instead of giving a reading, or the machine produces different samples, if could be a sign that the PBT is being influenced by RFI. If you see an officer using his radio near the PBT or having any of these problems, tell your attorney.

According to Virginia law, before conducting a PBT, the officer administering the test must notify the driver that 1) the test is voluntary and 2) the driver has the right to see the results of the PBT. If an officer does not tell the driver of these rights, or if the officer does not allow the driver to see the results of the PBT, then the PBT may not be used to justify an arrest.

Mouth Alcohol: Burping and Other Issues


Evidentiary Testing Devices (ETDs) assume that all the alcohol fumes they detect came from the driver’s lungs. Alcohol fumes from a person’s stomach, mouth, or throat are much more potent than the fumes from their lungs. A person who has recently consumed alcohol, burped, or vomited will produce a BAC breath result that is higher than normal.

Because of this problem, police officers in Virginia must observe the driver for 20 minutes before administering the breath test at the police station. During those 20 minutes, they are supposed to watch for signs that the driver has burped, placed anything in his mouth, or vomited. The officer administering the ETD breath test should request the driver to not burp, vomit, or place anything in his mouth before taking the test.

If the driver burps, vomits, or places anything in his mouth, the driver’s mouth must be cleaned out and the driver must be observed for another 20 minutes before testing. This procedure is extremely important, however not all operators consistently monitor drivers. If the operator did not monitor you for the full 20 minutes or if you burped, vomited, or regurgitated prior to testing, contact a local DUI attorney immediately.

Body Temperature


Breathalyzers do not take a person’s temperature; they simply assume the person’s body temperature is 98.6°Fahrenheit when calculating the BAC.  However, if the driver’s body temperature is over 98.6°, the machine will return an erroneously high BAC reading.

Anyone who has watched a pot of water boil knows that more water evaporates (steams) the warmer the water gets. Alcohol is the same. As the human body warms up, the percentage of alcohol vapors in the lungs rises. If a person has a fever, is dressed too warm, or is even left in a hot police car too long, the breath test may be erroneously high.

Deep Breaths/Blowing Too Hard


When someone has been drinking, there is more alcohol in the bottom of the lungs than there is in the top of the lungs. Also, as a person holds his breath, more and more alcohol evaporates into the lungs.

Studies have shown that a driver who holds his breath before blowing into a breathalyzer will increase the BAC reading, while a driver who hyperventilates will decrease the BAC results.

The police want you to take a great big breath and blow really hard, so that you exhale as much of that alcohol-rich air in the bottom of your lungs as possible. Often, an officer will stand over a driver and yell at him to blow harder. If a driver is forced by police to blow extremely hard it may cause the breath results to increase.



Breathalyzers do not actually measure a person’s blood alcohol content (BAC), they only estimate the BAC by measuring the amount of alcohol in a person’s breath. To estimate BAC based on breath alcohol, the breathalyzer uses a conversion number called a “partition ration” that is related to the rate at which alcohol evaporates from the blood into the lungs.

The partition ration that the INTOX EC/IR II’s uses is 2100, which is more or less the average partition ration for men. However, many women have a much lower partition ratio than men and thus have a much lower partition ration than the one used by the INOTX EC/IR II. (For women, the rate is closer to 1500.) This means that a woman with a BAC of .06% and a ratio of 1500:1 may produce a reading on the INTOX EC/IR II of .09%.

Machine Errors

There are many things that can interfere with a breathalyzer’s ability to take an accurate reading. While ETDs are much less susceptible to errors than PBTs, both suffer from the same potential problems.

Some typical machine errors include radio frequency interference (RFI), in which radio signals from officers’ communication devices strike the extremely sensitive voltammeter in the ETD or PBT and cause sporadic readings. The INTOX EC/IR II is designed to produce an “ambient detected” error message when RFI is detected, but the designers have not specified how consistent or accurate this feature is.

Bruises/Body Trauma

Blood samples taken at the hospital are often the key piece of evidence in a suspected DUI-related accident. Typically, hospitals use the enzymatic method for determining BAC, but this method may result in erroneously high readings that confuse serum alcohol (which is produced by tissue trauma) with ethyl alcohol. This means that drivers who sustain serious injuries in an accident may be falsely accused of being intoxicated when tested by the enzymatic method.

Check out our video “Virginia DUI Defenses”

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