Police are still working to confirm the identity of a body discovered Wednesday during the search for Jessica Ridgeway, a 10-year-old who disappeared Friday morning. If the body is Jessica's it would be a crime that is statistically rare.
According to a paper in the journal "Victims & Offenders," entitled "Sexually Motivated Child Abduction Murders: Synthesis of the Literature and Case Illustration," five or six children out of every million are murdered. That's equivalent to 0.0006 percent.
The FBI's Uniformed Crime Report counted 12,996 murder victims in 2010, the latest year for which final data was available. In that same year, the Census measured the population at 308,745,538. That would mean 0.0042 percent of the population was murdered.
That paper was authored by Kathleen Heidem, Eric Beauregard and Wade Myers from the University of South Florida.
They analyzed 621 child abduction murders and found that in 44 percent of cases, the victims were killed within an hour of the abduction. 74 percent were killed within three hours.
Most of the abductions, they found, were opportunistic. Only 14 percent of victims were selected, 86 percent were taken at random.
The murderers, the authors found, fell into two categories. One was a suspect who has sexually sadistic urges and is aroused by the murder. The other was murderers who killed the child to avoid apprehension and not specifically for sadistic gratification.
The killer tends to be males between the ages of 19 and 42, the authors found. He often has several past convictions and may previously have committed child sex abuse.
In a September 2012 interview, Forensic Psychologist Helinä Häkkänen-Nyholm at the University of Eastern Finland and University of Helsinki said that homicidal mutilation could be related to motivations including revenge or other strong emotions, losing touch with reality, lust and necro-sadism or a defensive action.