1. Assuming that driving behavior is related to alcohol consumption -weaving due to reaching for cell phone or other distraction but not because of intoxication.
2. Turning odor of alcohol into intoxication and using it as evidence of excessive consumption. Other factors that may cause an odor of alcohol include mouthwash, denture solutions, or having an alcoholic drink accidentally spilled on one's clothes, minimal consumption, etc.
3. Failing to ask pertinent questions about driver's medical problems – many medical issues imitate clues of intoxication or are too personal to discuss with DWI cop.
Officer fails to explain how past medical issues that you no longer consider a disability can cause you to fail to perform the test to his satisfaction.
4. Failing to disqualify persons who are physically unable to pass the SFSTs. A great number of persons cannot pass these exercises even while totally sober. The officer has no comparison of how you would perform the same test on your best day.
5. Being aware of, but failing to eliminate, distractions during SFSTs such as loose gravel, surfaces that are not level, environmental issues (misting, wind blowing, darkness), flashing lights, etc. These factors are under his control since he picks the time and place for the testing.
6. Failing to give proper instructions during the instructional phase of the SFST's. If any one of the SFST elements is changed, the validity of the test is compromised! Officers will later say that he "substantially complied" even though any deviation on your part results in failure.
7. Failure to give proper instructions during the administration phase of the exercise – if any of the SFST elements is changed, the validity is compromised! The Officer must give proper instructions and demonstrate the test to the citizen in the proper manner before the Walk and Turn Test and One Leg Stand Test can be performed. If the Instructions or Demonstration is done incorrectly by the officer then the results cannot legitimately be used against the citizen.
8. Failure to follow proper sequence of the SFST as per NHTSA Manual – if any of the SFST elements is changed, the validity is compromised! The officer cannot just make it up as he goes, although this is how many officers do their job.
9.. Administering invalid “tests” which are not supported by research studies – the officers are using exercises which have a 50/50 reliability rate (flip a coin). Many DWI cops will use tasks that they know have been rejected by the researchers and are not part of the Standardized program.
10. Tricking the person/driver to take the breath test by suggesting they will be released if they pass the test. Also, reading the paperwork to the person incorrectly or using outdated paperwork - renders the breath test result suppressible. Believe it or not, there are rules that the cops must follow in order to get the breath test results into a courtroom.