Bokpresentation What does it mean to be a ”perpetrator” of an offence and what does it mean to be an “accomplice”? What is the nature of that to which someone can be an accomplice and is it really necessary to distinguish between “perpetrators” and “accomplices”? These are some of the difficult issues that must be addressed in the law of “Parties to a Crime” (Täterschaft und Teilnahme). In trying to come to terms with this complicated part of general penal law the author makes use of a new approach. Although all the major schools of thought in this field are examined, the emphasis is on three contemporary, but completely different, alternatives to dealing with Parties to a Crime, from three jurisdictions. These alternatives are the Model Penal code, as a representative of Anglo-American law, the Swedish Penal Code, as a representative of Scandinavian law and finally, the reasoning developed by Professor Claus Roxin in his book, “Täterschaft und Tatherrschaft”, as a representative of the German theory of “hegemony and control over the act” (Tatherrschaftslehre). After an in-depth analysis of, and comparison between, these three alternatives, where each alternative is extensively criticized from different perspectives, the author proposes a new compromise solution to the law of Parties to a Crime. ---------- Vad betyder det att vara “gärningsman” respektive ”medverkande” vid ett brott? Hur definieras den handling som någon kan vara medverkande till, och är det nödvändigt att skilja mellan ”gärningsman” och ”medverkande”? Författaren inventerar gällande åsiktsriktningar inom allmän straffrätt samt jämför hur tre samtida men mycket olika rättssystem (amerikansk, svensk och tysk) hanterar frågorna. Därefter ges ett nytt förslag till lagen om medverkan. Boken är skriven på engelska.