In the United States, the number of homicides where the victim and offender relationship was undetermined has been increasing since 1999 but has not reached the levels experienced in the early 1990s. In 14% of all murders, the victim and the offender were strangers. Spouses and family members made up about 15% of all victims, about one-third of the victims were acquaintances of the assailant, and the victim and offender relationship was undetermined in over one-third of homicides. Gun involvement in homicides were gang-related homicides which increased after 1980, homicides that occurred during the commission of a felony which increased from 55% in 1985 to 77% in 2005, homicides resulting from arguments which declined to the lowest levels recorded recently, and homicides resulting from other circumstances which remained relatively constant. Because gang killing has become a normal part of inner cities, many including police hold preconceptions about the causes of death in inner cities. When a death is labeled gang-related it lowers the chances that it will be investigated and increases the chances that the perpetrator will remain at large. In addition, victims of gang killings often determine the priority a case will be given by police. Jenkins (1988) argues that many serial murder cases remain unknown to police and that cases involving Black offenders and victims are especially likely to escape official attention.[