In California, the arresting officer must tell you that you have the right to choose between different types of tests for alcohol. This usually means the choice between a Chemical Breath test, or a blood test. You will probably be given a series of field sobriety tests, such as walking a straight line and reciting the alphabet before being asked for a more scientific analysis. In some states you will be asked to perform a breathalyzer which measures gases in the breath. These results are susceptible to numerous problems, including false positives from people with diabetes and those who have worked with volatile chemicals. If you are offered a choice of tests, it is generally agreed that blood tests are the most accurate.  The information contained in this message is general and should not substitute for the advice and counsel of a licensed attorney.