If pulled over and you have an odor of alcohol, you may(will) be asked to look at a pen, walk a line and stand on one leg. Should you?

Think about it. How often do you do these tasks? And how often do you do them on a road? These field tests are completely voluntary and will only incriminate you.

With this in mind, how should one react when told to do these? Politely ask if they're required by law and kindly decline. It's that simple.