Articles Posted in Sobriety Tests for BAC/ Implied Consent

A Story:

Michelle was involved in a serious accident at an Orange County intersection. Witnesses reported that Michelle caused the accident when she ran a red light. The occupant of the vehicle Michelle hit was killed. Michelle was injured and transported by ambulance to the hospital. At the hospital, a nurse administered a narcotic to Michelle to subdue her pain. The narcotic affected Michelle’s awareness.

Shortly after she arrived at the hospital, a police officer who was assigned to investigate the accident responded to Michelle’s hospital bed to question her about the accident. As the officer spoke with Michelle, he believed he smelled the odor of alcohol on her breath. The officer asks Michelle if she had been drinking prior to the accident. Michelle told the officer she had one glass of wine with dinner an hour before the accident. The officer asks Michelle to submit to a breathalyzer test, but given her compromised state, she was unable to complete the test. Due to the effect of the narcotics, the officer was unable to ascertain whether she was under the influence prior to her arrival at the hospital.

The vehicle code, section 23152(b) makes it unlawful to drive with “0.08 percent or more, by weight, of alcohol in [a driver’s] blood.” You might immediately note that most DUIs are charged based on a breathalyzer measurement, not a blood measurement. I previously discussed how breathalyzers measure the alcohol content in a person’s blood but to complicate matters, the alcohol weight in a person’s breath must be translated into an equivalent blood weight measurement . If you continue reading section 23152(b) it states, “percent, by weight, of alcohol in a person’s blood is based upon grams of alcohol per 100 milliliters of blood or grams of alcohol per 210 liters of breath.”

These different measurements of alcohol by weight depending on whether the test was of blood or breath is known as “partition ratio variability.” The more accurate measurement of BAC is by measurement of alcohol content in the blood. Breath analysis loses some accuracy and though rigorous scientific testing, test established that the average amount of alcohol in 230 liters of breath is equivalent to what would be found in the 100 milliliters of the same subject’s blood. This may vary from person to person on either side of the scale. To allow for possible variations among individuals and to give the benefit of the doubt to the driver, the California legislature, set the conversion at 210 liters of breath to 100 milliliters of blood, or a ratio of 2,100 to one.

Before it was amended in 1990, section 23152(b) defined blood alcohol concentration (BAC) only in terms of “grams of alcohol per 100 milliliters of blood.” Because, then as now, many DUI charges were based on breathalyzer results, the breath results had to be converted using the standard 2,100 to one ratio. But because the partition ratio was not written into the statute, a common DUI defense was based on the effect of partition ratio variability factors. Following amendment of the law, the California Supreme Court held that the amended language was meant to criminalize driving with the specified blood alcohol level or the specified breath-alcohol level. In other words, the amendment did not simply provide an alternate method for calculating BAC but was meant to make it unlawful to drive with an .08 percent or more BAC as measured per 210 liters of breath.

The primary roadside tool used by law enforcement officers in the enforcement of DUI laws is the Preliminary Breath Test (PBT) or Preliminary Alcohol Screening (PAS) breathalyzer device. These small devices can be easily held in one hand. The officer instructs the driver blow into a mouthpiece on the device. This testis conducted twice enabling the officer to confirm a consistent result. Remember, in California, a driver does not have to submit to a roadside breathalyzer test unless he or she has been arrested. And even after an arrest, the driver still is not required to submit to the roadside test but may request a blood test or a breath test on the more accurate breath testing machine located in all law enforcement stations. The breath test machines at police stations are larger devices and produce more accurate results than the roadside devices. Despite some of the stories you may have heard, it is virtually impossible to fool the roadside breathalyzer or the breath testing machine at the police station.

All blood alcohol content breath testing machines use either fuel cell or infrared cell technology. The cell sensors on the machines oxidize the alcohol in the breath sample, which produces an electrical current that the breathalyzer is able to measure and translate into the percentage of alcohol in the persons system. Unless you are a chemist, this all sounds rather confusing but it may be enough to say that the alcohol in a person’s blood vaporizes and passes through the lungs. I discussed this process in an earlier post. These organic compounds passing through the lungs are measurable as wavelengths of alcohol.

Breathalyzers can produce inaccurate results. This may occur when the machine itself is not properly calibrated or defective. False-positive results may also appear on the machine due to the presence of alcoholic compounds in a person’s system that show up as ethyl alcohol molecules—the molecules that the breathalyzer detects—when, in fact, the alcohol molecules detected are part of the wider spectrum of methyl alcohol. Ethyl alcohol, the compound that is found in alcoholic drinks is only one molecule in a broader array of alcoholic compounds. For example, a person who suffers from certain medical conditions or who is taking a prescription medication may test positive on an alcohol detection breath test even though he or she has not been drinking. However, there are newer devices being put into operation that are able to distinguish between these various methyl alcohol compounds.

The use of roadside sobriety tests (Field Sobriety Tests or FSTs) for the detection of marijuana influence in drivers is not supported by current research and studies. The Massachusetts Supreme Court recognized this in a recent decision concerning an officer’s testimony on an alleged marijuana-influenced driver’s FST performance. The court held that FSTs have limited value in determining whether a driver is under the influence of marijuana. Following this decision, while an officer in Massachusetts may testify as to his or her observations of a driver’s performance on FSTs, the officer cannot testify as to his or her opinion that the driver’s performance on the FSTs indicated impairment due to marijuana intoxication. The court’s decision was limited to officers who are not qualified as experts leaving the holding somewhat vague as to the testimony of an officer trained as a drug recognition expert (DRE). Like California, Massachusetts legalized recreational use of marijuana last year but driving under the influence of marijuana remains illegal.

The decision is particularly interesting in its review of the numerous studies on the efficacy of FSTs as a tool to detect marijuana impairment. Acknowledging the disparate conclusions among studies regarding marijuana’s effect on driver performance, the court observed that a significant number of the studies have reached the conclusion that marijuana consumption can impair a driver’s performance. However, the court’s review of studies that seek to determine whether a driver’s performance on FSTs is a reliable indicator of marijuana impairment yielded mixed results and different studies have produced contradicting results. As the court noted, studies suggest that the typical FSTs are inadequate indicators of marijuana impairment.

While there is no scientific agreement of the efficacy of FSTs to detect marijuana impairment, the court noted that an officer’s observations still have value when considered with other evidence. However, the court found that FSTs—as far as driving under the influence of marijuana is concerned—currently have no scientific foundation and should therefore not be treated as scientific evidence that a driver was under the influence of marijuana.

Now that recreational marijuana is legal in California, law enforcement agencies are racing to train officers in roadside drug recognition. Since pot became legal, the Orange County crime lab has seen a 40 percent increase in requests to process blood samples related to driving under the influence of marijuana arrests. Whether there actually is an increase in marijuana-influenced drivers or the cops have increased their suspicions since legalization, one thing is for sure: the roadside detection of driving under the influence of marijuana is much harder for the cops than figuring out if a driver is under the influence of alcohol. Hence, the rush to train more officers as drug recognition experts.

The officers, who are trained to become drug recognition experts, receive an advanced certification which allows them to testify in court as an expert. While the specific focus on driving under the influence of marijuana is prompting the rush to certify more experts, these experts are trained to recognize symptoms of not only Cannabis use, but of six other categories of drugs:

  • Central Nervous System Depressants (examples include commonly prescribed drugs such as Prozac, Zoloft, and Paxil);


After an enjoyable dinner party where several bottles of wine were opened—feeling full in body and mind, but not particularly feeling effects of that wine, or so you think—you hop into your car and head home. A couple of blocks from home, you see one of Orange County’s finest flashing emergency lights behind you. The scream of the siren follows shortly thereafter. Your mind races. Did I drink too much? Why am I being pulled over? Am I going to get a DUI?

The outcome may depend on your response and even if you are arrested, the way you handle yourself during the vehicle stop is crucial. The first thing you must do is safely pull over using the appropriate turn indicator as you pull over. Don’t think that because you are only blocks from home, you can pull into your driveway and be legally “safe.” It is a common misconception that the police cannot arrest you without a warrant on private property.


One of the first things an officer will ask a driver to do when he or she suspects the driver is under the influence is to perform field sobriety tests or FSTs for short. In California, drivers are not required to submit to these tests but the officer is not required to inform the driver that the tests are not required. Consequently, most drivers will submit to the tests, either thinking they must or because they are afraid to say no, or because they believe they can pass the FSTs and be on their merry way (that’s a false assumption). FSTs are almost designed to be failed—even many entirely sober people will “fail” the tests—and the only real purpose of FSTs is to give the officer a reason to arrest the driver and to provide the prosecution with evidence.

But how accurate are FSTs anyway? The Standardized Field Sobriety Test, which is endorsed by the National Highway Traffic and Safety Administration (NHTSA), and used in California, consists of three separate tests: The Horizontal Gaze Nystagmus (HGN), the Walk and Turn (WAT). and the One-Leg Stand (OLS). The HGN measures eye movements in which the officer is looking for three indicators that suggest alcohol impairment. The WAT is the one most people associate with roadside drunk driving tests: the driver is asked to walk heel-to-toe in a straight line and to return in the same manner. The OLS requires the driver to stand with one foot approximately six inches off the ground and to count to 30. Any swaying, loss of balance, or inability to stay on one foot for 30 seconds may indicate alcohol impairment. According to the NHTSA, these three tests accurately detect alcohol impairment in 91% of all cases. According to the NHTSA, non-standard FSTs are unreliable.


In strange DUI news, Tostitos, yeah, the corn chips, is marketing a limited-edition “Party Safe” version of its Tostitos chip bag that …. get this: serves as a breathalyzer. Well, not really a breathalyzer but the bag contains a sensor that will detect alcohol on a person’s breath. If the sensor detects alcohol on the person’s breath, the bag’s logo design that includes a green circle will turn the circle red with a warning message “Don’t Drink and Drive.” An Uber code, which can be tapped by a smartphone to send out a driver to the location (using near-filed communication technology) will also appear on the bag. And in order to entice the drinker to call Uber instead of driving, the Uber code includes a discounted Uber ride. Gimmicky, you bet. But Tostitos (and Uber) may be on to something.

While this particular technology is rudimentary and doesn’t actually measure the blood alcohol content, as a breathalyzer does, it does detect whether there is alcohol on a person’s breath. You might surmise that the person already knows if he or she has been drinking, but this serves as a not-so-subtle reminder that maybe they shouldn’t be driving. The Tostitos bag was produced in limited quantities specifically for the Super Bowl but might this be a harbinger of things to come?


You’ve seen the ankle bracelets that some people are ordered by the court to wear to monitor their whereabouts while under house arrest. And you are probably aware of the Ignition Interlock Devices (IID) that are being ordered in many counties in California after conviction on a DUI. Here’s a new one that will probably become a new tool in the state’s ever sophisticated ways to regulate drunk driving: Wearable Blood Alcohol Monitors.

Several wearable blood alcohol monitors have been developed and will soon be available to law enforcement and the public. One of these devices—a type of skin patch— has been developed by UC San Diego engineers. It is described as a “temporary tattoo” that sticks to the skin and electrochemically detects alcohol levels through the wearer’s sweat. Maybe they decided to describe it as a “tattoo” rather than a skin patch to make it sound more appealing. In order to read the results, a small electronic circuit board is connected to the tattoo by a magnet and the results are communicated via Bluetooth.


On June 23, 2016, the United States Supreme Court issued a decision in the case Birchfield v. North Dakota, which will affect California’s “implied consent” DUI laws. The Court held that the Fourth Amendment to the United States Constitution permits a DUI breath test incident to an arrest without the need for a warrant but a warrantless blood test is unconstitutional. Both are considered a search governed by the Fourth Amendment but the Supreme Court found its decision on a privacy rights analysis vis-a-vis the need to obtain a BAC reading. Finding that a breath test is not a significant intrusion on one’s privacy but the piercing of skin and extraction of a part of the subject’s body is, the Supreme Court held that the extraction of blood to measure BAC is not a reasonable alternative in light of the availability of the less intrusive method.

The case was not just an academic exercise; the Supreme Court took this case in order to decide if states can make it a crime to refuse BAC chemical testing. Based on the Court’s analysis, the Supreme’s held that a motorist under arrest for DUI cannot be held criminally liable for refusing a blood test but can be held criminally liable for refusing a breath test.