Pennsylvania cops may not conduct a warrantless search of your car, unless the circumstances are sufficient to justify this. Take a look at California v. Hodari D. for the alternative, federal rule. A Pennsylvania police officer cannot send an informant into your home to beam your conversations out to the police. Again, Article 1, Section 8 provides a reasonable expectation of privacy in the home. Not so where Uncle Sam is concerned.
Federal law says silence can be used to impeach.
Some may be tempted to reply that these protections only benefit the criminals. This objection, however, misses the point. The protections of individual liberty found in the Pennsylvania constitution protect anyone who is accused of a crime. One hopes that those charged with crimes are generally guilty, in a moral sense, of actually having committed the evil deed with which they are charged. But these robust protections of individual liberty should properly be seen as robust limits on the powers of the government.