If the authorities have reasonable grounds to think you were the driver at the time of a traffic collision, they may administer a breathalyzer test to you. There is no need to suspect that you have alcohol in your system. The police can stop and arrest anyone for any crime, even if there is not enough evidence to prosecute them. Police officers need only have an articulable reason to believe that you have been driving under the influence of alcohol or drugs. This would include having witnessed any kind of motor vehicle violation committed by you, such as speeding or failing to use a turn signal. It also includes observing signs of intoxication such as being unable to stand without support or falling down when asked how many drinks you had earlier.
In some states, the police can stop you simply because you have an open container of alcohol in your car. They do not need to suspect you of drinking before stopping you. Open containers of alcohol are seen by some drivers as evidence that they have been drinking and should not be driving. If arrested for a DUI, it will be up to the officer to determine whether or not you were actually impaired by alcohol. He or she must make this judgment based on their experience and observation of your behavior.
Most states require that you be given notice that you will be subject to a chemical test before you are asked to submit to one.
The officer has grounds to think that you were the person driving/attempting to drive/in command of a motor vehicle involved in an accident. This implies that the police cannot just pull you over and demand a breath test at any moment. They must have reasonable grounds for believing that you were the driver.
In addition, the police officer must tell you why he or she is asking for your breath sample. If the officer doesn't give you this opportunity, then your consent is not valid. However, even if the officer does give you this chance, it isn't always enough to prove your innocence. For example, an officer could have suspicions about another driver but not want to delay the investigation by calling for a tow truck or taking other measures needed to ensure the safety of all road users.
In such cases, the officer would need further proof that you were indeed driving before demanding a breath sample. This might include seeing your license, car registration, or finding other evidence that proves your identity. Without this evidence, it is impossible to determine whether or not your refusal to take the test was justified.
People often claim that they weren't behind the wheel when they are pulled over by the police. In fact, there are several ways for an officer to know for sure who was driving including looking at passenger behavior, vehicle registration, and license plates.
After a night of drinking, a friend of mine once went into a police station the next morning and asked if he could take a breathalyzer test to see whether he could drive. They allowed him to do it. An officer cannot issue you a BA since they would be informing you that you are safe to drive. However, an officer can tell from smelling your breath or seeing how you react to questioning that there is alcohol in your system. This means that you cannot drive safely and should not be doing so.
Also, when taking a breathalyzer test, there is a chance that you might fail. If this happens, you will need to go to court with a lawyer and prove why you should not have been arrested.
Finally, even if you pass the test, this does not mean that you are free to drive. Police officers can decide not to give you a license, especially if you have been drinking.
So, yes, you can ask for a breathalyzer test from a cop.
Once a police officer has shown probable cause, he can request that the driver submit to a blood, urine, or breath test at a police station or a nearby hospital. A motorist may decline the test, but under "implied consent" rules, anybody who refuses the test may be deemed guilty. The Supreme Court has held that even if the driver is not under arrest, refusal to take the test may be used as evidence of guilt.
Also under "implied consent" laws, if you are involved in a car accident in any state where alcohol testing is allowed, then you have submitted to a blood alcohol content (BAC) test by law unless you refuse the test. If you fail the test, your license will be revoked for one year in most states. Some states also impose penalties if you have a BAC over the legal limit.
A breathalyzer test is very accurate in determining blood alcohol content. It works on the principle of infrared spectroscopy. Alcohol absorbs certain wavelengths of light, which can be measured by placing a sample of air into the machine itself. The machine gives a reading of how much alcohol is in your blood by comparing the wavelength of light it detects from your breath with a standard reading on a color-coded display. A blood alcohol content below 0.08% means you are not legally drunk in most states. In others, such as California and Nevada, being under the influence of alcohol is considered a crime even if you are under the 0.