A stop and frisk may be supported by a statement of an officer other than the arresting officer that the investigee is wanted for the commission of a crime. However evidence must be offered at the suppression hearing establishing the articulable facts that support the reasonable suspicion. In other words, the suppression court cannot speculate as to whether the officer who conveys the information to the arresting officer had sufficient facts to establish a reasonable suspicion; the officer who gave the information to the arresting officer must testify so that the court can determine whether police had reasonable suspicion to stop and frisk the defendant.

Third party bystanders do not give up their right to be free from unreasonable searches and seizures merely due to their presence at the scene of an arrest.

A warrantless seizure is illegal when the defendant is not engaged in any activity at the time of a stop that would have caused a person of reasonable caution to believe that the defendant was currently engaged in criminal conduct. Leaving a house that is a target of an investigation does not constitute reasonable suspicion. Suspicion that someone was involved in illegal activity at a time and location wholly separate from the police stop provides no basis for a Terry stop.

A person who appears to observe a police vehicle, then begins walking quickly away from a group of people on a street corner with a visible bulge on his or her person cannot be subjected to an investigatory detention, as this behavior does not give rise to reasonable suspicion.

For a Terry stop to be legitimate, the police must prove that specific conduct of the seized person, as observed by police, justified and made reasonable their belief that criminal activity was afoot and that the seized person was armed and dangerous.

A police officer may rely upon information that is broadcast over a police radio in order to justify an investigatory stop, but the identification information needs to be specific enough to reasonably conclude that the party being stopped is actually the person for whom he or she is searching. An overly general description will not support a Terry stop and frisk in the absence of suspicious behavior observed by the investigating officer, and radio call descriptions are typically not sufficient for reasonable suspicion.

"[W]here police officers observe unusual conduct which leads [them] reasonably to conclude in light of [their] experience that criminal activity may be afoot and that the persons with whom [they] are dealing may be armed and presently dangerous, where in the course of investigating this behavior the officer makes their status as a [law enforcement official] known and makes reasonable inquiries, and where nothing in the initial stages of the encounter serves to dispel [a] reasonable fear for [the officer's] own or others' safety, [the officer] is entitled for [his or her own] protection . . . and [the protection of] others in the area to conduct a carefully limited search of the outer clothing of such persons in an attempt to discover weapons which might be used in an assault. Such a search is a reasonable search under the Fourth Amendment, and any weapons seized may properly be introduced in evidence against the person from whom they were taken.

Once a motion to suppress is filed, the burden lies with the Commonwealth to establish, by a preponderance of the evidence, that the evidence sought to be suppressed is admissible.

A nonexhaustive list of factors to consider in weighing whether a seizure has occurred includes: the presence or absence of police excesses; whether there was physical contact; whether police directed the defendant's movements; police demeanor and manner of expression; the location of the interdiction; the content of the questions and statements; the existence and character of the initial investigative detention, including its degree of coerciveness; the presence of an express admonition to the effect that the defendant is free to depart is a potent, objective factor; and whether the citizen has been informed that he is not required to consent to the search.

The territorial jurisdiction of housing authority police officers is limited to the borders of the Authority's property and grounds and the adjoining property. Housing authority police officers employed by municipal housing authorities are not "municipal police officers" and therefore do not have extra-territorial powers under the Municipal Police Jurisdiction Act.