"The suppression of evidence favorable to the accused violates due process where the evidence is material either to guilt or punishment, irrespective of the good faith or bad faith of the prosecution. . . . Society wins not only when the guilty are convicted but when criminal trials are fair; our system of the administration of justice suffers when any accused is treated unfairly. An inscription on the walls of the Department of Justice states the proposition candidly for the federal domain: 'The United States wins its point whenever justice is done its citizens in the courts.'"

The Commonwealth may conduct separate prosecutions for drug transactions that were being investigated by different law enforcement agencies, though they occurred over a two-week period, even if both agencies are using the same informant. The logical relationship and potential for duplication of the facts are less vital concerns when different law enforcement agencies are investigating the same individual.

Eighteen burglaries in differing counties over 17 days did not constitute a single criminal episode requiring compulsory joinder, even though all the burglaries were residential and the defendant confessed to all of them at once.

The process of an adjudicatory hearing creates the same "anxiety and insecurity" and "heavy personal strain" as a traditional criminal prosecution. The consequences of social stigma and deprivation of liberty are also similar. Therefore, juvenile adjudications are subject to the double jeopardy clause. Jeopardy attaches when the court begins taking evidence.

Two offenses are not "the same" for double jeopardy cases if each offense requires proof of a fact that the other does not.

A BB gun is a "deadly weapon" under the meaning of that term in the Juvenile Act because it is capable of producing death or serious bodily injury.

Self-defense must be disproved by the Commonwealth beyond a reasonable doubt if there is "any evidence that will support the [self-defense] claim."

A court reviewing a decision not to decertify a case will reverse only upon "a misapplication of the law or an exercise of manifestly unreasonable judgment based on partiality, prejudice or ill will."

The decertification provisions of the Juvenile Act are not unconstitutionally vague, nor does placing the burden on the juvenile to show amenability to treatment offend the constitution.

A finder of fact should always be made aware when a prosecution witness may be biased because of outstanding criminal charges or another nonfinal disposition such as probation. Therefore, these topics are properly the subject of cross-examination.