Brass knuckles are hand-to-hand combat weapons fitted to the aggressor's fingers. Their shape resembles four large rings glued together. They are usually made of metal, such as steel and brass, or hardened plastic such as lexan. The severe damage they can cause, combined with their compact size (making surprise attacks easier), render them extremely dangerous. Pennsylvania law prohibits the possession, use and sale of brass knuckles, regarding them as a "prohibited offensive weapon."
According to Pennsylvania Consolidated Statute Title 18, Section 908 ("Prohibited offensive weapons"), it is unlawful for anyone to "make repairs, sell or otherwise deal in, use or possess any offensive weapon." Such offensive weapons include all firearms and also a number of dangerous articles, with "metal knuckles" explicitly mentioned in Paragraph C ("Definitions") of the section. Brass knuckles are, therefore, illegal in the Commonwealth of Pennsylvania.
Paragraph B of Section 908 lists exceptions to the statute. It is a defense to prove "by a preponderance of evidence" (balance of probabilities -- more likely to be true than not true) that a defendant owned the brass knuckles as a "curio," or collector's item. In addition, a defendant can also attempt to prove that the brass knuckles were intended for a "dramatic performance" (used by actors on a stage).
It is also a valid defense to show evidence that a defendant possessed the brass knuckles only briefly in consequence of having found them. Perhaps he removed them from an aggressor to avoid being hit with them. Paragraph B of Section 908 suggests a defendant can also invoke any "circumstances similarly negativing (disproving) any intent or likelihood that the weapon would be used unlawfully."
Individuals violating Section 908 are guilty of a "misdemeanor of the first degree." According to Title 18, Section 106 ("Classes of offenses"), a first degree misdemeanor for a violation under Title 18 is punishable by up to five years of imprisonment. If, however, a defendant used brass knuckles to seriously injure or even kill another person, he can be convicted of a felony, or even murder, under Section 106 and receive a longer sentence.