Understanding Field Sobriety Tests and Breathalyzer Usage in DUI Cases

Logan Anderson

Updated Thursday, June 13, 2024 at 7:35 AM CDT

Understanding Field Sobriety Tests and Breathalyzer Usage in DUI Cases

Field Sobriety Tests: An Initial Screening Tool

Field sobriety tests are commonly employed by law enforcement as an initial screening method to assess a driver's impairment. These tests are less cumbersome in terms of paperwork compared to using a breathalyzer, making them a preferred first step for many officers. When an individual is pulled over, the officer may ask them to perform a series of physical and cognitive tasks designed to detect signs of impairment, such as walking in a straight line or reciting the alphabet backwards.

Passing a field sobriety test can sometimes lead to the officer deciding not to administer a breathalyzer, thereby avoiding additional paperwork. However, if the individual fails the test, officers have probable cause to take them in for processing and perform further tests at the facility. This two-step process ensures that only those who show clear signs of impairment undergo more rigorous testing.

Probable Cause and Breath Tests

In the United States, probable cause or the individual's consent is required to administer a breath test. There are two types of breath tests: a field breathalyzer test, which is not admissible in court, and an intoxilyzer test, which is conducted at the police station and is considered more reliable. Field breathalyzer tests are voluntary and are primarily used to establish probable cause for arrest.

Refusing to take any test after arrest can result in a suspended license in many states. Police need probable cause to arrest someone and take them into custody for accurate testing, which is why the initial field sobriety test is so crucial. The most accurate blood alcohol concentration (BAC) measurements come from station breathalyzers or blood tests, not from the handheld units used in the field.

Accuracy and Limitations of Field Breathalyzers

Field breathalyzer units are not highly accurate and do not detect non-alcohol impairments such as those caused by marijuana or pharmaceuticals. This limitation makes field sobriety tests a critical component in gathering evidence for probable cause. However, these tests are subjective and can be influenced by various factors such as dyslexia or inner ear issues, which do not necessarily indicate impairment.

In the UK, refusing a breathalyzer test is grounds for detention to obtain a blood sample. Unlike in the US, failing to perform field sobriety tests like reciting the alphabet backwards is not a basis for arrest in the UK. This highlights the differences in how field sobriety tests and breathalyzer usage are handled in different jurisdictions.

The Role of Field Sobriety Tests in Establishing Probable Cause

Field sobriety tests can highlight erratic behavior, strengthening the officer's case for probable cause. Without a handheld breathalyzer, it is challenging to compel someone to go to a station or hospital for further testing based solely on driving behavior. These tests can be tailored to be sufficiently complicated, making it easier for officers to justify taking someone into custody.

The breathalyzer at the station is larger and not portable, requiring custody for its use. The evidence collected from field sobriety tests is later used in court to justify custody and further testing. Officers use these tests to gather enough evidence to establish probable cause before making an arrest, ensuring that the process is both fair and thorough.

Field sobriety tests and breathalyzer usage play crucial roles in DUI cases. While field sobriety tests serve as an initial screening tool, breathalyzers provide more accurate BAC measurements. Understanding the nuances of these methods can help individuals better navigate the complexities of DUI laws and their enforcement.

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