DUI Police Stop Procedure - Probable Cause
A police officer can pull over and conduct a traffic stop on a vehicle if they have a reasonable suspicion that a crime has or is being committed or they have witnessed a driver committing a traffic violation.
For example, if a police officer witnesses a vehicle swerving across lanes, driving too slow or too fast or driving erratically then this would give them a reasonable suspicion that the driver of the vehicle may be impaired by alcohol.
While reasonable suspicion is enough for an officer to conduct a traffic stop, they will need probable cause to make an arrest.
Once a vehicle has been stopped a police officer will investigate further. It is during this stage of a traffic stop that a person may give the officer probable cause for an arrest.
An officer conducting a traffic stop will be observing the drivers behavior closely looking out for signs of alcohol consumption and impairment. The smell of alcohol, slurred speech, glazed eyes, open containers in the vehicle or the drivers admission to consuming alcohol all go towards giving the officer a probable cause for arrest.
Field Sobriety Tests
Suspected drunk drivers may be asked to perform a field sobriety test (FST). Field sobriety tests are used to help an officer establish probable cause and find signs of impairment.
A lot of people are unaware that in the majority of states these tests are completely voluntary and a driver is well within their rights to politely refuse to take a field sobriety test if they are over the age of 21 and are not on parole.
While taking a field sobriety test is usually voluntary, it is worth noting that refusing to do so can help and officer establish probable cause for a DUI arrest.
Field sobriety tests may include the following:
Defined as 'an involuntary rapid movement of the eyeball, which may be horizontal, vertical, rotatory, or mixed.' Alcohol slows down the eyes ability to rapidly track objects and causes to eyes to oscillate or 'jerk' before they normally would in a sober person.
Alcohol stimulates the nerve endings, making nystagmus more pronounced in intoxicated persons. As a person's blood alcohol concentration increases, the eyes will 'jerk' sooner as they move to the side. The Nystagmus test claims to gauge intoxication by measuring the involuntary oscillation of the eyes.
During a nystagmus test, the police officer will position an object (usually a pen) approximately 12 inches away from a suspected drunk drivers face. He will then move the object from side to side, all the while watching the suspects eyes for an involuntary jerking movement as described above.
Walk and Turn
The police officer will first demonstrate the test while giving verbal instructions on how to perform the test to the suspect. The police officer will then ask the suspect if he understands the test and what is required before the test is initiated.
The police officer will then tell the suspect to take 9 heel-to-toe steps down a straight line. The suspected dunk driver will be instructed on how to correctly turn after the initial 9 steps have been taken.
A proper turn is taken with a series of small steps which again the police officer demonstrates. The suspect is then instructed to take another series of 9 heel-to-toe steps back to the starting position.
The police officer will instruct the suspected drunk driver to keep their arms by their side, watch their feet at all times, and count each step out loud. The suspect is directed not to stop until the test is completed.
Standing on One Leg
The police officer will instruct the suspected drunk driver to stand with their heels together before raising one leg at least six inches off the ground while their arms remain by their side.
The suspect will also be instructed to count out loud and switch legs. The police officer will be looking for obvious signs of difficulty in performing this test from the suspect such as raising their arms, losing their balance, hopping, swaying and other signs of impairment.
Finger to Nose
The suspected drunk driver will be instructed to place their feet together before tilting their head back slightly with their eyes closed. They will then be instructed to touch their nose.
All the time the officer will be looking for obvious difficulty from the driver in carrying out the test such as losing their balance, the inability to touch their nose, swaying, eyelid tremors, body tremors and other signs of impairment.
The Rhomberg Balance Test
During this test, the suspected drunk driver will be instructed to stand straight, close their eyes and tilt their head backwards for 30 seconds.
The officer will be looking for obvious signs of difficulty from the suspect in carrying out this test such as loss of balance, inability to stand still, body and eyelid tremors, swaying, muscle tension and other signs of impairment.
Preliminary Alcohol Screening
During a traffic stop an officer may request that a suspect take a preliminary alcohol screening (PAS) test. Like field sobriety tests, a preliminary alcohol screening test is used to help establish probable cause for an arrest.
A portable hand-held breathalyzer is used to carry out a preliminary alcohol screening test. The suspect will be required to blow into a preliminary breath testing (PBT) device. The device will then give an indication to the officer as to whether or not the alcohol level of a suspect is likely to exceed the legal limit.
The portable hand-held breathalyzer devices used to carry out preliminary alcohol screening tests are not as accurate as evidential breath testing (EBT) devices and are used by law enforcement as a screening device at the road-side only.
If the police officer gathers enough evidence to establish probable cause for an arrest, the suspect will be arrested for suspicion of DUI and will be required to submit to a chemical test of their blood, urine or breath in order to determine their blood alcohol content (BAC).
All states have implied consent laws. When a person applies for and receives a drivers license and when a person drives a vehicle on a public road or highway, by these actions they have given their implied consent to submit to a chemical test when required to do so by law enforcement officers.
Refusing to take a chemical test is an offense and often carries harsher penalties than that of being convicted of DUI. Penalties for refusing a chemical test include jail time, license suspension / revocation and ignition interlock restrictions.