The anatomy of a DUI arrest.

Police arrest thousands of motorists each year on suspicion of DUI. But not all motorists are convicted of this crime. The main reason is a strong DUI defense. But to build a strong DUI defense, we first need to understand the criteria police use to arrest a drunk driver.

Stated another way, we need to understand the steps police take to arrest a suspected drunk driver. We can then use these steps to build a DUI defense that is unique to each case. And this approach increases the chances a defendant will get a favorable outcome in his or her case.

To this end, police divide the DUI-arrest process into three phases:

  • First, the officer watches how the motorist drives;
  • Second, the officer make contact with the driver; and
  • Third, the driver performs field-sobriety tests.

Above all, police gather proof the driver is DUI in each phase. This includes recording these events with body and dash cameras. Prosecutors then use this evidence to convict motorists of DUI.

However, a close look at each step uncovers the outline for a strong DUI defense. And the first question a driver should always ask is: “Why did the cop pull me over?” The answer lies in phase one of this process.

DUI Phase One: Driving Violations.

In phase one, police do two things. First, they watch how the driver operates the car. Second, they watch how the driver stops the car. During each step, police look for evidence of DUI. But at the same time, the traffic stop is not always connected to a DUI violation.

For instance, police often stop DUI drivers for:

  • Speeding;
  • Weaving in the lane;
  • Drifting in the lane;
  • Driving a car with a burned out brake lamps; or
  • Driving a car with an expired registration.

In these examples, speeding, burned out brake lamps, and expired registrations provide little or no proof the driver is DUI. Sober and drunk drivers both commit these types of traffic crimes. This may become an important fact in a DUI case. Especially in cases where the driver looks good on the dash camera video and has a low breath-test score.

Moreover, police look for twenty-four (24) cues that create suspicion a driver is DUI. The table below lists these cues. The key is to provide an innocent explanation for these errors. The prosecutor will tell the jury these cues show the motorist is DUI. In contrast, the defense will need to tell the jury why this is not evidence of DUI.

Finally, let’s talk about the Fourth Amendment in DUI cases before we move on. Police need a legal reason to pull you over. If they do not have one, then this is an illegal search and seizure. Therefore, you should file a motion to suppress because police violated your legal rights. This is true even if police later learn that you are DUI.

Table 1: DUI and DWI Evidence Cues.

These are the cues police use to detect and arrest suspected drunk drivers.

They are divided into three groups: (1) problems maintaining a proper lane; (2) speed and braking problems; and (3) judgment problems.

No.DUI and DWI CuesType
1Weaving: The driver zig-zags on the roadway.Problem maintaining alane.
2Weaving across lane lines: An extreme case of weaving. Here, the driver actually crosses the lane lines before correcting his lane position.Problem maintaining a lane.
3Straddling a lane line: Driver operates vehicle with lane marker in between the left and right wheels.Problem maintaining a lane.
4Swerving: An abrupt turn away from a straight course.Problem maintaining a lane.
5.Turning with a wide radius.Problem maintaining a lane.
6.Drifting: Driving car at an angle.Problem maintaining a lane.
7.Almost striking another car or object.Problem maintaining a lane.
8.Stopping problems: Stopping too far, too short, or too jerky.Speed and braking problems.
9.Quickly speeding up or slowing down.Speed and braking problems.
10.Changing speeds: Switching between speeding up and slowing down.Speed and braking problems.
11.Driving slowly: Driving 10 mph below the posted speed limit.Speed and braking problems.
12.Driving in the opposing lane or driving the wrong way on a one-way street.Vigilance problems.
13.Slow response to traffic signals: Driver stopped at a green light.Vigilance problems.
14.Slow or failure to respond to the officer's signals.Vigilance problems.
15.Stopping in lane for no apparent reason: Where there is no traffic signal, emergency situation, or a traffic condition to justify the stop. In other words, the driver just isn't moving.Vigilance problems.
16.Driving with headlights turned off at night.Vigilance problems.
17.Failing to use turn signal or using turn signal that is inconsistent with actions.Vigilance problems.
18.Following another car too closely: i.e., tailgating.Judgment problems.
19.Unsafe lange changes.Judgment problems.
20.Illegal turns.Judgment problems.
21.Driving car on other than a roadway: Driving on the shoulder, off the road, or through a turn only lane.Judgment problems.
22.Stopping inappropriately in response to officer's overhead lights.Judgment problems.
23.Inappropriate or unusual behavior: Drinking in the car, urinating at the roadside, or arguing without cause.Judgment problems.
24.Appearing to be impaired.Judgment problems.

DUI Phase One: Stopping Sequence.

Next, police watch how a driver responds to the traffic stop. In particular, police look for the following cues in this step:

  • Whether the driver attempts to flee;
  • How slowly does the driver respond to the traffic stop;
  • Does the driver swerve abruptly;
  • How does the driver stop; and
  • Does the driver hit the curb during the stop.

The police theory is that alcohol makes it harder for drunk drivers to concentrate on both the driving and the police command to stop:

The signal to stop creates a new situation with which the driver must cope. Flashing emergency lights or a siren demand and divert a driver’s attention, requiring that the driver now divide attention between driving and responding to the stop command . . . An impaired driver may not be able to handle this more complex task and additional evidence of impairment may appear.

DWI Detection and Standardized Field Sobriety Testing, V-10 (2006).

Nevertheless, the defense can use this information at trial. If the driver did not commit any of these violations, then this is proof he drove sober. After all, only drunk drivers commit these violations. Right?

In the alternative, if the driver did these violations, then the defense must show sober drivers commit these violations too. The trial tactic will depend on the circumstances of each case.

Table 2: DUI and DWI Post-Stop Cues and Evidence

Police use these post-traffic stop cues as evidence to arrest and prosecute drivers on suspicion of DUI or DWI.

No.Description
1.The driver has difficulty controlling the vehicle.
2.The driver has difficulty exiting the vehicle.
3.The driver fumbles for his or her driver's license or proof of insurance.
4.The driver repeats questions or comments.
5.The driver sways, is unsteady on his feet, or has trouble staying balanced.
6.The driver leans on a vehicle or other object for support.
7.The driver has slurred speech.
8.The driver is slow to respond to the officer's questions or commands. Or, the officer must repeat himself (or herself).
9.The driver provides incorrect information. Or, the driver changes his or her answers.
10.The officer smells the odor of alcohol coming from the driver.

DUI Phase Two: Police speak with the driver.

During the second phase, the officer completes two tasks. First, the officer must observe and interview the driver. Most of all, the officer must decide if he (or she) is going to ask the driver to get out of the car. If the officer asks the driver to get out, then he must watch how the driver exits the car. This is step two.

Equally important in phase two, the officer looks for common DUI clues. They include watching for:

  • Bloodshot eyes;
  • Soiled clothing;
  • Open (or closed) alcohol containers;
  • Slurred speech; and
  • An odor of alcohol.

If the officer sees these clues, he will ask the driver to get out of the car. In effect, the officer already suspects the driver is DUI. The officer will then go to phase three.

However, similar to phase one, phase two also provides useful points for the defense. The defense can show what the driver did correctly: (1) he provided his driver’s license; (2) he provided proof of insurance; (3) he responded to the officer’s questions; and (4) he got out of the car without any problems. This is important because it shows the driver acted normally and drove sober.

DUI Defense Phase Three: Standard Field Sobriety Tests (SFST)

Standard field sobriety tests (SFST) are the three roadside tests police use in DUI cases. They include the HGN (eye) test, the Walk-and-Turn (WNT) test, and the One-Leg Stand (OLS) test. Police use these test to determine if a driver is DUI. Notably, the tables below outline the procedures for each test.

However, these tests have one thing in common. They are methods to measure a driver’s mental and physical impairment. But at the same time, they have two limitations. First, the officer must administer the tests correctly. Second, there are innocent reasons for failing these tets.

I want to focus on the second reason for a moment. The innocent reasons why drivers fail these tests. One example is poor health. Many people have bad knees or bad backs. This makes it difficult for them to stand on one leg, hold their balance, or walk a straight line. Another example is nervousness. Police stops are stressful. And many people do not perform well under stress. For this reason, stress is also an innocent reason for failing the tests.

Additionally, SFST are not based on normal behavior. People don’t stand on one leg for thirty seconds. People do not walk nine steps on an imaginary line. Jurors understand this. Therefore, the defense can show that these unusual tests do not show the driver was DUI.

Finally, the tables below show why innocent drivers “fail” these tests. Many drivers perform the SFSTs. They follow directions. They look good on video. In fact, they look normal. But then they are arrested for DUI. And they all have the same reaction. The arrest surprises the drivers. The culprit in SFSTs is the scoring. They are difficult to pass. And they are designed for failure.

Table 3: Horizontal Gaze Nystagmus (HGN) Clues

Nystagmus is an involuntary rapid oscillation of the eyes. Horizontal Gaze Nystagmus (HGN) is a variety of nystagmus that occurs when an individual's eyes are deviated to the lateral extreme. More importantly, alcohol and certain other drugs cause HGN.

According to the DWI manual, an officer must look for the three criteria listed below in each eye, for a total of six clues.

The officer does this by placing a stimulus, such as a penlight in front of the driver's eyes. Further, the stimulus is placed between 12-15 inches in front of the driver's nose during this test. If the officer observes four or more clues on the HGN test, then the officer classifies the driver as intoxicated.

At the same time, the officer must perform the HGN test correctly before the results are admissible in court. This is a big issue in many DUI and DWI cases. Police frequently botch the HGN test.

Therefore, the defense is often able to exclude the HGN test results at trial. See Emerson v. State, 880 S.W.2d 759, 769 (Tex. Crim. App. 1994) (En Banc) (requiring police to follow standardized procedures before HGN results are admissible at trial).

No.HGN CluesViolations
1.Lack of smooth pursuit.The officer sees the driver's eye(s) jerking or bouncing as they follow the officer's penlight.
2Distinct and sustained nystagmus at maximum deviation.The officer moves the penlight to the driver's maximum field of vision on both the right and left side of the driver's face.

Usually no white is showing from the corner of the driver's eye.

The officer then holds the penlight for four seconds on each eye. And the officer looks for pronounced jerking or bouncing in the eye.
3.Onset of nystagmus prior to a 45 degree angle.Police move the penlight at a 45 degree angle at a 4 second interval.

If nystagmus occurs prior to reaching the 45 degree angle, then this is a clue the driver is intoxicated.

Table 4: Walk-and-Turn Clues (WNT)

The Walk-and-Turn test is one of three standardized tests police use to detect drunk drivers.

In this test, police give the driver the following instructions:

(1) "Place your left foot on the line" (Real or imaginary). The officer demonstrates this move;

(2) "Place your right foot on the line ahead of the left foot, with heel or right foot against toe of left foot." (Officer demonstrates this move);

(3) "Place your arms down at your sides." (Officer demonstrates this move);

(4) "Maintain this position until I have completed the instructions. Do not start to walk until I [tell] you so;" and

(5) "Do you understand the instructions so far?"

The officer then demonstrates the WNT test. Specifically, the officer tells the driver to "take nine heel-to-toe steps, turn, and take nine heel-to-toe steps back."

Police look for the clues listed below. If they see two or more clues, then the driver is classified as intoxicated.

No.Walk-and-Turn CluesViolations
1.Person cannot keep balance while listening to the instructions.The officer records this clue if the person cannot maintain the heel-to-toe position during the instruction stage.
2.Person starts the test before the officer finishes giving the instructions.The officer records this clue if the person starts walking before the officer tells driver to begin.
3.Person stops while walking heel-to-toe.The officer records this clue if the person pauses for several seconds.
4.Person does not touch heel-to-toe during the test.The officer records this clue if the person leaves a space greater than .5 inches.
5.Person steps off the line.The officer counts clue if one foot is completely off the line.
6.Person uses arms for balance during the test.The person raises one or both arms more than 6 inches from the sides in order to maintain balance.
7.Person turns improperly.This occurs when the person removes the front foot from the line while turning. Or when the person "spins" or "pivots" around.
8.Person takes incorrect number of steps.Finally, this clue happens when the person takes more than or less than 9 heel-to-toe steps in either direction.

Table 5: One-Leg Stand Clues (OLG)

The one-leg-stand test is the third standardized field sobriety test police use to detect and arrest drunk drivers.

During this test, the officer tells the person to stand with his feet together and his arms down at his sides. The officer then instructs the person to raise one foot (either one) six inches off the ground. Finally, the officer tells the person to count out loud for 30 seconds with his foot off the ground.

If the officer sees two or more clues during the OLG test, then the person is classified as intoxicated.

No.One-leg Stand CluesViolations
1.The person sways while balancing.This clue means side-to-side or back-and-forth motions while the person maintains the one-leg stand position.
2.The person uses arms for balance during the test.Occurs when person moves arms six or more inches from the side of his body in order to keep balance.
3.The person hops during the test.The person keeps one foot on ground. But he hops to maintain balance.
4.The person puts foot down during the test.The person puts his foot down one or more times before the 30 seconds expire.

DUI Defense: Breathalyzer and Blood Alcohol Tests

DUI Defense. DPS DIC-24 Form.
DIC-24 is the form police use to request a breath or blood specimen of a driver arrested for DUI.

Unfortunately, police routinely arrest drivers for failing SFSTs. This brings us to our final stage in the DUI-arrest process–the breath or blood test.

After police arrest a driver for DUI in Texas, they request the driver blow into a breathalyzer. This machine measures the amount of alcohol in a driver’s system. More importantly, the officer reads the driver a legal warning called a DIC-24. The DIC-24 is pictured above. In short, this warning tells the driver what will happen if the driver does not provide a breath sample.

San Antonio, Texas DUI Defense

A DUI arrest is a stressful. Drivers face potential jail time and fines. DPS may also suspend your driver’s license. Also, many first time DUI offenders do not have a criminal record. This makes the DUI journey scary. However, understanding the DUI process is an important first step in this journey.

This knowledge allows the driver to explore his or her options. In some cases, the three phases described above may prove the driver is DUI. But in other cases, the evidence may show the driver is sober and not guilty of DUI. In these cases, the driver should plead not guilty and go to trial. Because it is not illegal to have a drink and then drive. It is only illegal to drive while you are intoxicated. Or as one writer put it, “A man may drink and not be drunk[.]”

Law Office of Genaro R. Cortez, P.L.L.C.

730 West Hildebrand Avenue
Suite 2,
San Antonio, Texas 78212
Phone: 210-733-7575
Fax: 210-733-7578
Email: genaro.cortez@cortezlawyer.org