The basic definition for driving under the influence (DUI) or driving while intoxicated (DWI) is the crime of driving a motor vehicle while impaired by alcohol or other drugs (including those prescribed by physicians), to a level that renders the driver incapable of operating a motor vehicle safely.
If you’ve been charged with a DUI or DWI, one of the ways to collect evidence against you will be with a urine sample. This post will provide information on how alcohol affects the body, spreads via the blood stream, and is eventually used as a tool to convict you with a DUI/DWI charge.
The Path Into the Urine: A Physiology Sampler
Alcohol is very hydrophilic (water loving), and once absorbed into the system distributes in the body based on the water concentration of the organ/substance. The blood travels to the lungs where there is an exchange of gasses, and alcohol is passed from the blood to the lungs. At the same time, the blood is filtered in the kidneys, and passes into the formation of the urine.
The kidneys perform a necessary function in the human body. Metabolic waste products and excess water and sodium in the blood are eliminated from the body via the kidneys. Blood enters the kidney via the renal artery, which branches to feed segments of the kidney. Blood is filtered by the kidney though a structure called the nephrons. Each of the almost one million nephrons receives blood vessels into their round structure, called the Bowman’s capsule.
The capsule filters out blood cells and large molecules (larger than 70,000 MW) such as proteins, keeping these substances in the blood stream. Water, glucose, amino acids, urea, sodium, chloride, and potassium are filtered at the glomerulus (a tuft of capillaries). The clear filtrate leaves the Bowman’s capsule to a structure known as the loop of Henle, which extracts many of the substances, such as glucose, amino acids, sodium and potassium and allows them to be reabsorbed. In fact, about 2/3 of that filtered is reabsorbed, including about 80% of the filtered water.
The fluid from the nephrons then passes into a collecting duct, which passes the fluid through the kidneys. The formed urine flows down the muscular tubes known as the ureters, and through a sphincter into the bladder. As urine accumulates in the bladder, the bladder walls expand, eventually sending a nerve signal to the brain to void the bladder. Generally, the urge to urinate appears when there is about 150-300 ml of urine in the bladder. In 24 hours, 600 to 2500 ml may be excreted.
After absorption into the blood, alcohol begins to be metabolized in the liver. Over 90% of the ingested alcohol that circulates in the blood stream is oxidized in the liver. Almost 10% is excreted unchanged from the body, including via the lungs or urine. About 0.7-1.5% of the amount consumed is excreted unchanged in urine.
Collecting the Sample
The conversion ratio of UAC to an equivalent BAC is dependent on the quality of the urine specimen collected. By far the most acceptable method of collection is to collect two samples, with the second void collected at least 20 minutes from the first void. This is because it takes time for the formation of urine from the blood filtering through the kidneys, and the urine alcohol level lags behind the blood alcohol level about 20 minutes. The second void is then tested and converted from the urine alcohol concentration (UAC) into an equivalent BAC.
The Reliabilty of the Sample
The use of urine as a forensic specimen is questionable. A urine analysis clearly can show the presence of alcohol, and recent consumption of alcohol. As such, it is a useful specimen in probation cases, or cases where the subject is prohibited from alcohol consumption. However, in determining driving impairment, the analyst should interpret urine specimen results with caution.
What Should I Do?
When facing a DUI arrest and offered a breath, blood, or urine test ALWAYS take the urine test. Why? Because of the three tests, urine tests are agreed to be the least reliable (making it more likely to be unadmissable as evidence against you).
If you’re facing a DUI charge, the first thing you should do is call a skilled criminal defense attorney who is an expert in DUI law. Driving Under the Influence (DUI) charges carry with them the possibility of both jail time and the loss of driving privileges. As with any criminal case, a DUI defendant makes a major mistake if he attempts to make their way through the system without an aggressive criminal defense lawyer to stand up for their rights. Contact Monder Law today for a free San Diego DUI attorney initial consultation regarding your case. Vik Monder represents clients in throughout San Diego.