There are pros and cons to taking a field sobriety test if you're asked to do so by the police or law enforcement in Pennsylvania. If you're not driving under the influence and if you're asked to take a field sobriety test, and if you could successfully complete the field sobriety test, the hope would be that the police would allow you to go on your way. If you are driving under the influence and you're not able to successfully complete the field sobriety tests, the prosecution would be able to use evidence of the failed tests in the DUI case against you.
If you're driving under the influence and if you're able to pass the field sobriety tests and the police do not, let's say, have probable cause otherwise to arrest you, then you may be allowed to go on your way. It may be an unlikely scenario, however, based on just how police generally investigate and address DUI stops. If you refuse to take the field sobriety test, in all likelihood, the police or law enforcement would arrest the person for suspicion of DUI. It may be that they have less to use against the person in a DUI case, so that would be a potential benefit obviously.
If you're charged with a DUI, the stakes are high, you need to have an experienced Pennsylvania DUI attorney in your corner from as early as possible in the process to help you best understand and navigate the criminal process.