If the police violate the law during your traffic stop, anything that they learn, gain, or find as evidence by law can’t be used against you. The term we learned in law school that we like to say is it’s the fruit of the poisonous tree, but what that just means is that it was something they gained as the result of illegal conduct. Texas law says that any evidence the police gain as the result of illegal police conduct cannot be used as evidence against you.
So if the police pull you over and they don’t have reasonable suspicion that you committed a crime then that stop is illegal. If they detain you and they don’t have reasonable suspicion, say that you’re intoxicated if it’s a DWI, then when they detain you and try to get you to do some tests on the side of the road that’s illegal and that can’t be used against you If they then arrest you without probable cause that also is illegal and anything they gain after that say a blood test is illegally obtained; cannot be used against you.