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Challenging breath test results in DUI cases

On Behalf of | Mar 6, 2024 | Dui/dwai |

Toxicology test results usually provide prosecutors in Colorado and around the country with their most compelling evidence in drunk driving cases. Juries tend to be swayed by scientific evidence as it is objective rather than subjective, but it is not infallible. The devices used by law enforcement to measure blood alcohol concentrations are extremely sophisticated and accurate, but they have to be maintained according to strict protocols. When they are not, the results they provide can be challenged in court.

Set up and calibration

Breath-testing equipment can provide unreliable results if it is not set up correctly. When a New Jersey state trooper made a mistake during this procedure, more than 18,000 breath tests were invalidated. Breath-testing devices are electronic measuring instruments, which means they must be properly calibrated or the results they produce could be inaccurate. Police departments often neglect to perform this important task, which can lead to thousands of tests becoming inadmissible in court. When a motorist in Massachusetts questioned the validity of a breath-test result, the ensuing chain of events led a judge to exclude every breath test conducted in the state for eight years.

Probable cause

Colorado’s implied consent law requires motorists suspected of operating their vehicles while under the influence of alcohol to submit to chemical testing, but police officers must have probable cause to request a breath test. If a police officer acts without probable cause, a judge may determine that ordering a breath test violated the Fourth Amendment’s protection against unreasonable search and seizure. This would likely lead to a drunk driving charge being dismissed.

Plea agreements

Most drivers facing DUI charges choose to enter into plea agreements because they believe the evidence against them is overwhelming. While toxicology test results provide prosecutors with compelling scientific evidence, they are not always accurate. If police officers do not have probable cause to order breath tests or breath-testing devices are not set up properly and calibrated regularly, toxicology evidence could be challenged in court and may be excluded.

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