The Constitution of the Commonwealth of Pennsylvania, as well as the Fourth Amendment of the United States Constitution, protect citizens against unlawful searches and seizures, including arrests. When it comes to criminal defense, Fourth Amendment protections are foundational. In order to overcome these protections, a law enforcement officer, according to the language of the Amendment itself, must have “probable cause” before searching or seizing a person, their home or their property.

Even a search or an arrest warrant is not immune from the probable cause requirement. On the contrary, in order to obtain a warrant to search a person or premises, or to arrest someone, a law enforcement officer must submit a sworn affidavit that enough probable cause exists to overcome a person’s Fourth Amendment rights. A judge will examine the affidavit and weigh the evidence, and if sufficient probable cause exists, sign the warrant.

Probable cause is determined on a case-by-case basis by looking at the totality of the circumstances. It needs to be more than a “hunch” or a suspicion on the part of a law enforcement officer. There must be a combination of facts and circumstances known to the officer – at the time an arrest or seizure is made or an application for a warrant is submitted – that demonstrate that a crime has been committed or may be committed. If there was no probable cause to arrest or search prior to the arrest or search, evidence found afterward cannot be used to justify the Fourth Amendment violation.

Challenges to probable cause are a cornerstone of defending the rights of those who face criminal charges. Law enforcement searches or detentions without sufficient probable cause occur so frequently than an entire body of case law has evolved around the issue.

Source: FindLaw.com, “Probable Cause,” accessed Apr. 3, 2018