Proof Issues in DUI-Marijuana Cases
Chemical tests are very reliable in DUI-alcohol cases. But a reliable chemical test in DUI-marijuana cases remains elusive. The same researchers who hit a brick wall in 2023 now believe that a reliable marijuana Breathalyzer device may be within reach. However, even if they develop such a test, legal issues, such as what level of marijuana in the bloodstream intoxicated a person, must be ironed out.
So, for the foreseeable future, prosecutors must continue to rely on circumstantial evidence in DUI-marijuana cases. As outlined below, this circumstantial evidence has some serious weaknesses that a Leesburg criminal defense lawyer can exploit. The stakes are high. A single DUI conviction usually costs more than $20,000. Higher auto insurance rates account for most of that cost. Challenging the circumstantial evidence in a DUI-drug case is the best way, and usually the only way, to prevent a DUI conviction from staining a driver’s permanent record.
Vision Evaluation
An HGN (horizontal gaze nystagmus) and VGN (vertical gaze nystagmus) evaluation is usually the first field test that police officers perform in DUI-marijuana cases.
Quite simply, nystagmus is an involuntary pupil movement at certain viewing angles. Most people have probably taken a “follow my finger” nystagmus test at some point, most likely in a doctor’s office.
These controlled condition nystagmus tests are extremely accurate. But roadside HGN tests are different because the conditions are completely uncontrolled. That’s especially true for nighttime DUI stops. Flashing strobe lights atop nearby squad cars when they shine against a dark sky severely impair an officer’s ability to see involuntary pupil movement.
Furthermore, marijuana use isn’t the only cause, or even the leading cause, of nystagmus. Generally, a mild childhood brain injury causes nystagmus. Typically, the symptoms are so mild that most people don’t know they have this condition. Therefore, they couldn’t pass a nystagmus test under any circumstances.
For these and other reasons most Loudoun County judges don’t allow prosecutors to use eye test results as proof of guilt. Instead, judges restrict these test results to preliminary matters only.
Divided Attention Tests
Intoxicated individuals don’t have the mental capacity to multitask. They can only focus on one task at a time. That’s the main reason driving while intoxicated is so dangerous. Two tests, the walk-and-turn and the one-leg stand, usually determine the suspect’s ability to multitask, and therefore, the degree of drug impairment.
The walk-and-turn test isn’t just walking a straight line. Officers require subjects to walk a certain number of steps forward and backward. They also often include other instructions as well, such as instructing subjects to count out loud or not count out loud.
Likewise, the one-leg stand test has similar elements. The subject must elevate either the left or right leg, hold the leg at a certain angle, and keep the leg steady for a certain amount of time.
Many defendants cannot follow these directions, but that doesn’t necessarily mean the subject is intoxicated. Other issues, such as nervousness or fatigue, could also impair the ability to listen to and follow directions. That’s especially true if English isn’t the subject’s first language.
Connect With a Thorough Loudoun County Lawyer
There’s a big difference between an arrest and a conviction in criminal law. For a confidential consultation with an experienced criminal defense attorney in Leesburg, contact Simms Showers, LLP, Attorneys at Law. Virtual, home, and after-hours visits are available.
Source:
nist.gov/news-events/news/2024/08/nist-researchers-test-new-approach-detecting-cannabis-breath
