Testimony concerning a pre-trial photographic identification must be suppressed when the Commonwealth fails to retain the photographs that were utilized for the photographic line-up, thus making it impossible to review the fairness of the procedure challenged.

Post-indictment lineups are a critical stage of the prosecution at which the defendant is entitled to counsel. Both defendant and counsel should be notified of an impending lineup, and counsel's presence is a requisite to conducting the lineup, absent an intelligent waiver of that right by a defendant. When the defendant is deprived of counsel at the lineup, the proper remedy – after first giving the Government the opportunity to establish by clear and convincing evidence that subsequent identifications were obtained by means purged of the primary taint – is to exclude the in-court identification evidence. In other words, although an out-of-court identification may be unlawful or suggestive, a subsequent in-court identification of an accused as the perpetrator may be admitted if it has a basis independent of the tainted identification.

A warrant is not a general investigatory tool. A reviewing court must determine what items there is probable cause to seize, and then assess the items sought in the warrant to determine whether they have been described as specifically as reasonably possible. An officer executing a warrant should have no discretion about what items to seize.

A magistrate may not consider any evidence outside the four corners of the affidavit of probable cause when deciding whether to issue a search warrant.

Mere police observation of a single exchange of an unidentified item or items on a public street corner for cash (which alone does not establish probable cause to arrest) cannot be added to, or melded with the fact of flight (which alone does not establish probable cause to arrest) to constitute probable cause to arrest.

The task of a magistrate issuing a warrant is simply to make a practical, common-sense decision whether, given all the circumstances set forth in the affidavit, including the "veracity" and "basis of knowledge" of persons supplying hearsay information, there is a fair probability that contraband or evidence of a crime will be found in a particular place.

For a consensual search to be deemed valid, the Commonwealth need not show that that the person subject to the search knew that he or she had the right to refuse such consent. Therefore, consent must be voluntary but it need not be knowing or intelligent.

A person with common authority over an area may consent to a police search of the premises; however if another who also has authority is present and objects, there is no valid consent to search.

Whether a consent to a search was in fact "voluntary" or was the product of duress or coercion, express or implied, is a question of fact to be determined from the totality of all the circumstances. While the subject's knowledge of a right to refuse is a factor to be taken into account, the prosecution is not required to demonstrate such knowledge as a prerequisite to establishing a voluntary consent.

Police may not create their own exigencies and then use them as justification for bypassing the warrant requirement. If the exigency arises because of unlawful behavior on the part of the police, such as their stopping someone in the absence of reasonable suspicion, then the exigency that is created does not justify the warrantless search.