By Veronica Fernandez-Alvarado
The Sacramento Bee
SACRAMENTO, Calif. — If you’re pulled over on suspicion of drunk driving in California, you might be asked to walk in a line, stand on one leg and follow an object with your eyes.
Across the Golden State, law enforcement officers use a number of methods to determine whether a driver is intoxicated.
What exactly are field sobriety tests? How accurate are they? And what are your rights as a driver?
The Sacramento Bee reached out to the Sacramento Police Department and legal experts to find out:
What is considered impaired driving under California law?
“It is illegal to drive while under the influence of alcohol or any drug that affects your ability to drive safely,” the California Department of Motor Vehicles said on its website.
Alcohol, cannabis, illegal drugs, prescription drugs and even over-the-counter medications can “all affect your ability to drive safely and react to what you see and hear,” the DMV said.
“Some prescription medications and over-the-counter drugs may interfere with driving,” the Rancho Cordova Police Department explained in a Facebook post. “While medicinal and recreational marijuana are legal, driving under the influence of marijuana is illegal.”
Law enforcement agencies across California frequently monitor roads for impaired drivers.
Sobriety checkpoints are funded through grants from the California Office of Traffic Safety, with funding from the National Highway Traffic Safety Administration.
How many DUI arrests are made in California?
In 2023, there were approximately 125,000 DUI-related arrests in California, according to the California Highway Patrol’s State Integrated Traffic Records System.
Statewide, there was an average of 4,542 alcohol-involved crashes resulting in fatalities and serious injuries per year from 2020 to 2024, according to DUI statistics from the UC Berkeley Transportation Injury Mapping System.
During that time period, Sacramento County had 217 fatal and serious injury crashes involving alcohol per year on average, DUI statistics showed, ranking it among the five worst counties for alcohol-related fatalities in the state.
Los Angeles County had the most alcohol-related fatal and serious injury crashes of any county in California, with an annual average of 735 crashes during the same time period, according to DUI statistics.
How do police tell if drivers are drunk?
Law enforcement agencies use a series of physical and mental exercises to determine whether drivers could be under the influence of alcohol or drugs.
These exercises, known as field sobriety tests, allow officers to gather evidence in case a DUI charge needs to be administered, according to Sacramento Police Officer Anthony Gamble.
The tests can also indicate to officers whether the driver should undergo a blood alcohol content test or a breath test to determine how much alcohol is present in their bloodstream, said Gamble.
Under California law, a blood alcohol content of 0.08% or higher is illegal for drivers 21 and over, while it’s illegal for drivers under 21 to have a blood alcohol content of 0.01% or higher, the Shouse California Law Group said.
“We do not perform (field sobriety tests) on every motorist stopped,” Gamble wrote in an email to The Sacramento Bee.
Law enforcement officers conduct tests “when we believe a motorist may be intoxicated based on objective signs of intoxication,” such as an erratic driving pattern, slurred speech, bloodshot eyes, an unsteady gait or a “strong odor of alcohol,” Gamble said.
What are field sobriety tests? What do they look like?
The National Highway Traffic Safety Administration developed standardized field sobriety tests in the late 1970s in an effort to improve the fatality rate on highways due to drunk driving, according to the Criminal Justice Institute.
The Southern California Research Institute determined that three specific tests, when administered in a standardized manner, were “highly accurate and reliable” methods for distinguishing blood alcohol content above 0.10%, according to Justia Legal Resources.
Law enforcement agencies nationwide use the same three tests: eye examination, walk-and-turn, and one-leg stand.
The eye examination test, also known as the horizontal gaze nystagmus test, involves an officer observing the eyes of a driver as they follow a moving object, according to Rathburn Law Office in Indianapolis.
“If your eyes jerk when following the object, it’s likely because you’re intoxicated,” the Indiana law office said on its website.
In the walk-and-turn test, the driver is asked to walk heel-to-toe on a line, then “return in the same manner,” according to the Law Office of John A. Campanella in Sacramento.
This allows the officer to assess the driver’s “ability to follow instructions, maintain balance and walk in a straight line,” the law firm said.
In the one-leg stand test, the driver stands on one leg while counting aloud for a specific duration of time. This test allows the officer to evaluate the driver’s balance, coordination and ability to follow directions, said Gamble.
“These tests have been studied scientifically and are standardized,” said Gamble, who previously worked as an instructor for DUI enforcement officers. “There are additional non-standardized field sobriety tests that may assist in an investigation, including (the) finger-to-nose test, alphabet test (and) Romberg test to name a few.”
How accurate are DUI tests?
According to Gamble, each of the three standard field sobriety tests has a likelihood of 79% or higher of indicating intoxication in a driver.
For instance, if law enforcement officers observe “four or more validated clues” during the eye examination, Gamble said there’s an 88% likelihood the driver has a blood alcohol concentration over 0.08%.
If officers observe clues on all three tests, there’s a 91% chance that the driver has a blood alcohol concentration over the legal limit, Gamble said.
Although police interpret failure to complete field sobriety tests as a sign of alcohol or drug consumption, critics caution that they’re not foolproof.
“Even though these tests are considered standard, it’s important to remember that they are flawed due to their subjective nature,” according to Cron, Israels & Stark Attorneys at Law, which has offices in Los Angeles and Santa Monica.
“A police officer’s opinion can be influenced, and it’s possible that the tests were not conducted exactly according to protocol,” the Southern California law firm said on its website. “Being aware of these potential challenges is key to understanding the process.”
In a 2007 article in scientific journal Law and Human Behavior, Steven Rubenzer wrote that the research supporting the use of these tests was “limited” and their reliability “mediocre.”
“Field sobriety tests are the only behavioral tests that, if failed, are likely to lead to arrest,” Rubenzer wrote.
Field sobriety tests can be less reliable when administered to people with disabilities that can affect balance, reflexes and sensory receptors, according to the Law Offices of Charles L. Waechter in Maryland, as well as overweight people, people with injuries and those 65 or older.
Can I refuse field sobriety tests?
Field sobriety tests are not mandatory, and there are no legal penalties for refusing them, according to Gamble.
Gamble said it’s important to note that officers do not rely solely on these tests to determine if someone is an impaired driver.
“Someone could very well be arrested for DUI without submitting to the (field sobriety tests) if the officer’s observations support the arrest,” he said.
What happens if you fail field sobriety tests?
If a law enforcement officer has “probable cause” to believe a driver is under the influence of intoxicants, the driver can be charged whether or not they perform a field sobriety test or submit to a breath test, Gamble said.
“The decision to arrest is based on the totality of circumstances of the interaction,” he explained, including “driving behavior” and “objective signs of intoxication.”
Under the California Vehicle Code, impaired drivers can be charged with driving under the influence of intoxicants or with driving with a blood alcohol content greater than .08%, Gamble said, noting that legal standards differ for each charge.
What’s the penalty for drunk driving?
If you are arrested on suspicion of driving under the influence of intoxicants, the DMV has the authority to revoke or suspend your license.
Drivers charged with a first-time DUI face an average of $13,500 in fines and penalties, as well as a suspended license.
So-called “repeat offenders” can face more serious consequences.
So can DUI drivers involved in crashes that result in injuries or death, according to the DMV and legal experts
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