The study conducted 247 police interviews and analyzed 1,414 West German records of resolved and unresolved criminal cases from 1977 to 1979. The results indicated that a crime is more likely to be resolved if witnesses or crucial information on the suspect emerge early in the investigation or if the case resembles earlier cases. After suspect identification, the following factors are crucial in the outcome of penal proceedings: the suspect's confession, victim or witness testimony, and circumstantial evidence. The study also shows that the West German legality principle influences the way the police investigate crime; this principle demands that the police must follow up on all reasonable suspicions. Although police may focus on investigating serious crimes, equality before the law demands that even less serious crimes or crimes which are less likely to be resolved must be investigated. The study finds the current West German application of the legality principle a fair and flexible guide in allocating police resources. A bibliography and glossary are included.