DUI Testing: SFSTs & Chemical BAC Tests
DUI Testing: SFSTs & Chemical BAC Tests
  • Standard Field Sobriety Tests (SFSTs)


    Officers typically have DUI suspects perform SFSTs when they believe a driver is DUI. SFSTs are not necessary to charge a DUI or for a DUI conviction. Further, a driver may refuse SFSTs without incurring a separate penalty. Nevertheless, these tests can be used to support an officer’s request for chemical testing and as evidence that the suspect was incapable of safely driving due to impairment.

    • DUI Alcohol SFSTs


      In alcohol cases, the police usually do the following tests:


      Horizontal Gaze Nystagmus (HGN), which is not admissible at trial; 1-leg stand; and, 9-step walk-and-turn. Further, the police will usually have the suspect blow into a preliminary breath test (PBT), which is inadmissible at trial.

      • PBT Testing - Inadmissible


        Here, it is also important to explain that a PBT test is used to indicate the presence of alcohol and/or give an approximate BAC reading. In short, PBTs are not calibrated machines. Admissible BAC breath tests are done on breathalyzer (Datamaster) machines at police stations or DUI booking centers. They are not portable devices. Breathalyzer machines offer admissible BAC evidence because they are calibrated machines that are tested for accuracy.  

    • DUI Controlled Substance SFSTs


      In controlled substance cases, ARIDE (Advanced Roadside Impaired Driving Enforcement) trained officers typically perform additional tests on the suspects eyes, such as: evaluating pupil size; vertical gaze nystagmus (VGN), to detect involuntary jerking of the eyes; lack of convergence (LOC), to detect an inability cross one’s eyes while following a stimulus; and, the modified Romberg balance test, to check a subject for eye and body tremors and their ability to estimate the passage of time and to balance their body.


      Here it is important to note that ARIDE training does not qualify an officer as a Drug Recognition Expert or Drug Recognition Evaluator (DRE). A DRE trained officer receives more rigorous education and is trained to perform a detailed evaluation on drivers suspected of being impaired. A DRE will perform an evaluation consisting of twelve steps and collect additional evidence that can be articulated as an opinion of whether one is impaired by drugs.

    • Challenging SFSTs


      Standard Field sobriety tests are not always accurate. Studies show that the tests are challenging for healthy sober individuals. These tests fail to accurately predict the legal intoxication level about 30 to 35% of the time.


      Moreover, Non-Standard Field Sobriety Tests (finger to nose, alphabet, counting backwards) are not considered valid predictors of intoxication.

      • SFSTs Instructions


        The instructions the police give to the accused are extremely important. The directions must be accurately given for the test to be conducted correctly. In short, if they are not properly given, the SFSTs cannot be reliable indictors of intoxication. Here it is important to review the MVR (if available) to evaluate if the instructions were correctly stated by the officer.

      • Age & Physical Condition


        These tests should not be given in certain circumstances depending on the accused age and/or physical condition. They are especially inaccurate if the person tested has injuries, health issues, is fifty (50) or more pounds overweight, or over the age of 65.

      • Location


        SFSTs must be conducted in safe and fair location and conditions (appropriate lighting, level surface, etc.) to have evidentiary value.  Where a field sobriety test was administered may unfairly impact the results. For a field sobriety test to be fair it should be given on a flat and dry surface. Field Sobriety tests should not be given on an incline, cracked or broken pavement, or during bad weather. If those conditions were present, the results may be inadmissible.

  • Chemical BAC Testing


    Pennsylvania allows testing of blood, breath, and/or urine to determine a DUI suspects BAC. For a BAC obtained via breath to be admissible, it must be measured by an approved breathalyzer machine that is calibrated and certified. As noted BAC obtained by a PBT is not admissible evidence. 


    BAC evidence may result from a chemical test properly requested by the police pursuant to the Implied Consent Law and the Fourth Amendment. A driver’s BAC can also be obtained by the police via search warrant or subpoena in situations where blood or urine were otherwise legally collected (medical treatment).  

    • Implied Consent Law


      The foundation of PA DUI law is the implied consent rule. This rule requires that anyone who drives a car in Pennsylvania is deemed to have given their consent to breath, blood, or urine chemical tests to determine if they are driving under the influence of alcohol or drugs. 


      A police officer may request a chemical test if they have “reasonable grounds” to believe that the licensee was operating or was in actual physical control of the movement of the vehicle while under the influence of alcohol or a controlled substance. Thus, the burden is low here and allows officers to request chemical testing on mere suspicion of DUI.


      Pennsylvania can punish drivers who refuse to submit to a breath or chemical test. Refusing the tests is unwise because the punishment is harsh — drivers who refuse the breath or chemical tests are treated as offenders with the highest rate of BAC and face additional driver’s license suspensions. 

      • Birchfield v. North Dakota


        On June 23, 2016, the United States decided Birchfield v. North Dakota. This case held that in the context of a DUI investigation, the police need a search warrant before a blood draw if the suspect is threatened with heightened criminal penalties if they refuse blood testing. The Birchfield Court decided that DUI breath tests do not require a search warrant.


        In response to Birchfield, PennDOT amended the refusal forms that officers are supposed to read to DUI suspects by deleting the language concerning the enhanced criminal penalty for test refusals.


        Nevertheless, in light of Birchfield, DUI cases must be closely analyzed on a case-by-case bases to determine if a blood or breath test was unreasonable in violation of the Fourth Amendment

    • DUI Refusals


      A driver will be charged with a DUI refusal when the suspect fails to fully comply with the implied consent law discussed above. In short, if an officer has reasonable grounds to request chemical testing, and the driver fails to fully comply with the test, it is considered a refusal.


      Refusal can be expressed or implied. An expressed refusal occurs when a suspect verbalizes their choice to refuse testing. A refusal may be implied by the suspect remaining silent or failure to fully submit to the testing. Full compliance means that the accused must blow into a breathalyzer machine as instructed so it may register a test result. Failure to comply with a test as instructed can result in an attempt being deemed as a refusal. 

      • Refusal Rights and Warnings


        A DUI suspect has the right to refuse chemical testing. However, there are sever consequences to exercising this right once an officer properly gives the suspect notice of the chemical test warnings.

        • Notice of Refusal Suspension


          An officer must notify a driver (by reading a form to the suspect) that refusing to submit to a chemical test will result in a driver’s license suspension.

        • No Right to Counsel


          Our courts have held that the right to counsel does not attach when a suspect is asked to comply with the implied consent law. Accordingly, a DUI suspect does not have the right to call a lawyer to gain counsel on whether they should submit to or refuse chemical testing.

      • Refusal Penalties

        • DUI Criminal Case


          A DUI suspect that was properly warned concerning the implied consent law will be penalized with the highest criminal DUI penalties. Here, it is important to note that a DUI refusal conviction always carries a license suspension.


          Further, evidence of the refusal is admissible at trial to prove the suspect was DUI. Accordingly, DUI refusal cases are typically more difficult to defend.

        • Refusal Suspensions


          If a DUI suspect refuses chemical testing, the police are required to file a report on the refusal to PennDOT. Upon receiving the notice, PennDOT will issue a letter to the driver informing them that their license will be suspended because of the refusal.


          Here, it is important to note that a refusal suspension is separate from any suspension related to the criminal DUI case. For example, a DUI refusal prosecution that is resolved with ARD will result in a total suspension of 1 year (the refusal suspension) and 60 days (the ARD suspension). Pursuant to the new ignition interlock rule, a driver in this situation may be able to drive earlier with an ILL license. 

        • PennDOT Refusal Appeals


          A driver subject to a refusal suspension has due process rights. As noted, PennDOT must give notice of the refusal suspension in writing. A driver has thirty (30) days to file an appeal in the Court of Common Pleas to challenge the refusal suspension. The appeal period runs from the mailing date of PennDOT’s letter, not from the suspension date, the date the letter was received, or any other date. The “mailing date” is noted at the top of PennDOT’s letter.


          A PennDOT appeal hearing is a civil case. It is completely independent from any criminal prosecution. At the hearing PennDOT must establish four elements to sustain a suspension of licensee’s operating privileges for refusing to submit to chemical testing: (1) a police officer arrested the licensee for DUI and had reasonable grounds to believe that the licensee was operating or was in actual physical control of the movement of the vehicle while under the influence of alcohol or a controlled substance; (2) the licensee was asked to submit to chemical testing; (3) the licensee refused to submit to the chemical testing; and (4) the licensee was warned that refusal to submit to the chemical testing might result in a suspension of his driver’s license. Banner v. Department of Transportation, 558 Pa. 439 (1999).


          While PennDOT’s burden of proof at a refusal hearing is low there are benefits to filing an appeal. There are cases where PennDOT cannot sustain their burden of proof and/or a strong legal argument favors the driver. Further, filing the appeal stays (delays) the imposition of the license suspension.     

      • Challenging Chemical Test BAC Results

        • Challenging Breathalyzer Test Results


          Breathalyzers are subject to challenge in Pennsylvania courts. there are procedures the police must follow to properly administer a DUI BAC test.

          • Machine not Calibrated or Certified


            The Commonwealth must establish that the breathalyzer machine was properly calibrated and certified. Failure to do so may lead to suppression or the evidence or it being inadmissible at trial.

          • Observation Period


            These tests require that the subject not eat or drink for 20 minutes before testing and after the time of the arrest. Therefore, when the police want to use a breath test they must conduct an observation period. Specifically, the police must keep the suspect under observation for twenty minutes prior to giving the breath testing. If they do not do this the results of the test may be inadmissible.

          • Unlicensed BAC Test Operator


            Under Pennsylvania law, a breath test operator must have be properly trained and possess a valid operator's license for the breath test results to be admissible. No license or an expired license can lead to no breath test results at trial.

          • Faulty Breath Test Machine or Misuse of Machine


            All machines malfunction, breath test machines are no exception. Likewise, a machine is only useful if it is used correctly. Therefore, it is important to analyze the machines history (repairs) and how the police used it. A breath test machine will not give correct results if improper settings were used or if it was simply a faulty device that gave inconsistent results. The burden is on the Commonwealth to show that the machine worked, was used properly, and the required procedures were followed. If the Commonwealth cannot prove this the results may not be used at trial.

          • Breath Test Machine False Readings


            Certain benign products people commonly use can interfere with and cause an elevated breath test result. Specifically, mouthwash, medication, cough drops and other everyday products can cause a false positive test. Radio frequency interference can also result in inaccurate readings.

        • Challenging Blood Test Results


          There are procedures that must be followed for the results of a BAC blood test to be admissible. Where, how, when, and by who the blood sample was taken, preserved, tested will determine if it is admissible. For example, the hospital or testing center must be certified and follow specific procedures. The test should be given within two hours of a person's arrest. Alcohol should not be wipes on the suspects are before the blood is taken. 

          • Product of Illegal Search


            If blood evidence was obtained in violation of the Fourth Amendment, it should be suppressed. Further, if blood is draw without probable case of that the subject was DUI, it should also be suppressed.

          • Chain of Custody


            Blood evidence must be properly handled and documented to be admissible. If the chain of custody is effectively challenged, the blood tests should be suppressed.

          • Absorption Phase Testing


            Alcohol takes time to absorb and dissipate in the human body. When the accused stopped drinking in relation to the time they were driving and then tested is also highly relevant and may be used to show the driver was not legally intoxicated.

          • Challenging Gas Chromatograph / BAC Analysis


            To analyze the blood sample and get a BAC result, it must be tested. This testing is called Gas Chromatography. Blood BAC test results can be challenged by questioning the instruments use, calibration, and maintenance. The formula used to arrive at the BAC should also be questioned because if the formula is wrong the BAC is also inaccurate.   

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