DUI stands for driving under the influence of alcohol or drugs. To test whether someone is intoxicated is done by measuring a person’s blood alcohol content or blood alcohol concentration referred to as BAC. This is calculated as a decimal figure. For example, the range of BAC goes from the lowest of .01 that indicates the consumption of alcohol is low to .04 or greater which means the person is very intoxicated.
Another type of test is the breath test which is used for alcohol detection because it is considered less invasive than drawing blood. The test is based upon the assumption that the concentration of alcohol in the breath exhaled is the same as the amount of alcohol inside the lungs.
Using hair close to the scalp is another way of measuring alcohol content by identifying chemical “markers” that are present when alcohol is consumed and remain in the hair if not cut or shaved. The more markers, the higher the alcohol consumption.
A saliva test is also used to detect alcohol by assuming the amount of alcohol in the saliva is the same as in the blood.
The urine test is mostly used for drug use. Marijuana can be detected up to 30 days after extensive usage. Alcohol can be detected up to a week of prior use.
Another type of blood test used by a crime lab for drug use is called a “GC-MS” (gas chromatography, mass spectrophotometry) which can identify a specific drug previously analyzed in their computer system.
Then there is the “Can-you-walk-in-a-straight-line?” test .
However, each test has its limitations and an individual arrested for DUI can get a good attorney to argue those points. Inaccuracies are sited in the BAC as a link broken in the “chain of custody” or procedures done in the testing process. The breath test can have a flaw in the assumption that the concentration of alcohol in the breath equals the amount in the lungs because changes can occur in that process. Gender and weight of the individual plus the type of alcohol consumed also plays a significant factor in the equation as well how the person tolerates alcohol. The urine test can be invalid if a person abstains or uses considerably less alcohol or drugs for a long enough time period for the substances to leave your body. This also goes for the hair test. The hair test could also be invalid if a person dyed or cut their hair or not enough hair is taken. Before a GC-MS test is given, a shorter version done on a different device can come out negative for certain common drugs and the more expensive test wouldn’t be given. For marijuana use, there are a number of products that can alter the above tests making a person look “clean”.
DUI laws vary for each state. It is important to contact the motor vehicle department immediately to avoid losing your license. The time frame to do this also varies for each state. It’s important to take the tests to avoid looking guilty. Conviction means losing your license, substantial fees or jail depending on the degree of the offense. The prosecutor (person trying to conviction you) will use driving patterns, physical symptoms, field sobriety tests and chemical test results against you. It often happens that your charge can be reduced or dropped because the prosecutor has to prove your guilt beyond a reasonable doubt which gives the advantage to your DUI lawyer and you, the plaintiff.
Here are terms and definitions you may need to know.