http://prtl.uhcl.edu/portal/page/portal/USN/TheSignal/Life?articleId=402
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*(1970s) - DR. Egger says, serial killers continue to kill because some aspect of the murder fulfills a psychological need, either the way in which the murder was committed, or what was done with the body afterwards.
Not only is it difficult to figure out why serial killers continue to kill, it is also hard for law enforcement agencies to identify a serial killer due to "linkage blindness," another term coined by Egger. "Police don't share information across jurisdictional boundaries," Egger said. "There's always some friction there." Agencies prefer to worry only about their own jurisdiction, instead of sharing information to work together to solve a murder.
Egger says a serial murder investigation may, but not always, have as many as seven different crime scenes: the place the victim was initially lured, transportation to a different location, the place the victim was kept, transportation to another location, where the victim was killed, where the body was dumped, and where the weapon was dumped. "In most instances all the police have is the dumpsite," Egger said. Egger says the other crime scenes are never investigated because of linkage blindness and the fact that law enforcement officials usually treat serial murder as a single homicide. "But if you find out that you're talking about multiple dumpsites in different jurisdictions, then you have a higher possibility of coming up with some trace evidence, particularly in the first kill," Egger said. "The offender brings something to the crime scene, leaves something at the crime scene, and takes something away from the crime scene,"
Egger said when explaining his three part premise of a crime scene and the reason there is not always a lot of trace evidence. "If you have someone who is aware of that, who is careful, and you're only dealing with one dumpsite, and you're treating it as a single homicide, you have no way of managing your suspects," Egger said. Egger says a typical homicide is not difficult to solve because you are simply dealing with people's alibis, and the person without one becomes the prime suspect. However, in a serial murder you do not have that. "All crime is serial in nature," Egger said.
"Most criminals, if not caught, will repeat their crime. And if that's true, then you've got to share information."