What legal argument might a defense raise against SFST evidence?

The defense can effectively argue against the evidence obtained from Standardized Field Sobriety Tests (SFST) by highlighting improper administration of the tests. SFSTs are designed with specific protocols that must be strictly followed to ensure their validity. If an officer fails to administer the tests correctly—such as not providing appropriate instructions, not ensuring a proper testing environment, or using one of the tests improperly—the integrity of the results is compromised.

When the tests are not conducted according to established guidelines set forth by the National Highway Traffic Safety Administration (NHTSA), it can lead to unreliable results. This creates a reasonable doubt about the driver's impairment, which can be pivotal in defending against DUI charges. The defense may also bring forth expert testimony to support the claim that test results were invalid due to these procedural errors, strengthening their argument in court.

This avenue of defense focuses on the procedural aspects of the testing rather than external factors like weather conditions, training background of the officer, or the duration of the stop, which, while potentially relevant, do not undermine the fundamental validity of the SFSTs in the same direct manner.