Police likely are pouring through hours of surveillance video taken at banks, gas stations, government buildings and elsewhere, Lanning said.
In Cody, Wyo., where an 11-year-old girl was abducted and sexually assaulted Oct. 8, police were able to get a license plate number from surveillance video at Yellowstone National Park that led them to a suspect in Montana. The girl was released hours after her abduction.
Investigators also have statistical data based on past crimes of this type that could provide a general profile of who may have committed the crime, Lanning and FBI profiler Clinton Van Zandt said.
Neither Lanning nor Van Zandt would provide an opinion on the Colorado case, saying each case is unique.
However, a 2006 report funded by the U.S. Department of Justice and compiled by Washington state Attorney General Rob McKenna determined the majority of suspects in such cases are single and between 18 and 30 years old.
The study looked at more than 800 cases from 1968 to 2002, the latest figures available. It found nearly half the suspects were unemployed, and those who did have jobs worked in unskilled or semi-skilled labor occupations.
The report also said 21 percent of victims were 10 to 12 years old and initially encountered their abductor within a quarter-mile of their home. Jessica was 10 and last seen within two blocks of her house.
Lanning and Van Zandt noted investigators will build their own suspect profile using the evidence. They'll consider where Jessica was last seen alive and where her body was found, along with the condition of her body, which police have said was "not intact." There's also the girl's backpack, which might contain clues.
"Behavior can be expressed in a crime scene," Lanning said. "We're greatly hoping that in addition to behavioral clues, how about he left his DNA?"
Lowery, of the National Center For Missing and Exploited Children, added that fewer children have been abducted and killed in recent years because of greater awareness and the Amber Alert system established nationwide in 2003. He said several abductors have released children after seeing or hearing such an alert.
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