If you're stopped while driving in Pennsylvania and the police officer asks you to do field a sobriety test, you do not have to perform the field sobriety test. That being said, would it be the better thing to do or not? It will depend on the circumstances. If you're not driving under the influence and the police officer asks you to do the field sobriety test because the police officer believes you'd be driving under the influence and if you could pass those tests, if the police officer is satisfied, he may allow you to go on your way. There's obviously a benefit in that. If you are driving under the influence and if you can pass the field sobriety tests and if the police officer has no other indication or probable cause that you're actually driving under the influence, you may also be free to go on your way or the police officer may allow you to go on your way.
If you are driving under the influence and you can't pass the field sobriety tests, the prosecution certainly will use that against you come the time of your DUI case. If you were to go to trial, for example. If you refuse to do so and if you find yourself going to trial, they could use your refusal to do so, the prosecution that is, as an indication that you were in fact driving under the influence. It can vary in terms of whether it's better to do the field sobriety test or not. Having an experienced Pennsylvania defense attorney will be able to help you best understand and navigate the DUI process and will be able to help you present the best possible defense.