A common defense is that the police officer was not legally justified in stopping a driver. Or, the police officer did not comply with the correct procedures during the DUI arrest. Any illegally seized evidence may be deemed inadmissible and weaken a criminal prosecution or lead to its dismissal. Likewise, defendants may challenge the arresting officer’s credibility, or the evidence collected during the stop. This requires convincing evidence. Video or witness testimony may support this defense.
Motorists may also attempt to challenge the accuracy of the breathalyzer or other chemical test. This can be effective if the breathalyzer device was ultimately found defective. But, even though breathalyzers are not always 100% effective, these devices are usually pretty useful at measuring a driver’s blood alcohol content level.
Witnesses can provide compelling evidence if they are able to competently testify that the motorist seemed sober when they drove, the driver did not drink right before getting in the vehicle or the driver has a medical condition that has symptoms that make them appear intoxicated, such as low blood sugar. To be credible, the witness should have been sober at the time of the arrest.
Drivers may also try to show that their appearance may have given the impression that they were intoxicated even though they were sober. For example, the driver did not perform well on the field sobriety tests because of physical impairments or injuries, or they had bloodshot eyes because of drowsiness, allergies or contacts. Additionally, speech may be slurred because of fatigue or medications, or the instructions on the field sobriety tests were unclear. But, valid blood, urine or breathalyzer tests performed at the stop may undercut these arguments.