There are signs... there are always signs

Not only your pupils, but I believe your tongue is also a sign- the color of. Also, they only have to pull you over for a legit reason to ask you to perform a sobriety test- it would be later you would be asked to take a urine test (if you were) and your refusal would be leading to the fact that you were guilty. You could still be charged with negilegent or wreckless driving. Is it worth it? I know I'm impaired while taking pain meds... I won't drive. I think you have to ask yourself if it's worth somebody's life, whether it be your own or somebody elses because you were under the influence. Ultimately, it's you that would have to live with your own conscience.