"I'm a strong believer that the community is an incredibly underrated and important resource for solving crimes, especially when the crimes are fresh," forensic psychiatrist Dr. Michael Welner told "Good Morning America" today. "You get the public mobilized to say ... 'What do you remember?'"
Investigators have sifted through nearly 2,000 leads in the case, but have yet to narrow in on a suspect. Authorities are now asking the public to think back to anything, even seemingly innocuous events, that might lead to Somer's killer.
"We're referring to people associated with the offender in this case," Clay County Sheriff Rick Beseler said. They likely don't realize they are associated with the killer, he said.
The Florida second-grader was buried Tuesday, a little more than a week after she disappeared while walking home from school. Her body was later found in a Georgia landfill.
Welner said the killer likely falls into one of two categories of pedophiles. He said there are visible pedophiles -- the people who are known to associate with children through coaching sports and volunteer work -- and the pedophiles you don't see. Pedophiles you don't see tend to behave normally in front of the public and have normal sexual relationships.
"Clearly there is a distinction between the pedophiles you see and the pedophiles you don't," Welner said. "The pedophiles you see may violate the children again and again and again. And the pedophiles you don't see violate and destroy."
The sheriff urged people to alert detectives if they notice certain changes in people's behavior, like "an unnatural interest" in the girl's case, or hiding their vehicle in a shed or giving it away.
"You will recognize the change and even question them about it but not realize it is associated" with the Somer Thompson case, Beseler said.
Beseler said telltale signs of someone who could have been involved with Somer's murder would be a combination of several behaviorial changes, including:
Leaving the area unexpectedly.
Having missed work or other routine engagements, especially on Oct. 19, the day Somer disappeared.
Unexplained injuries such as cuts or bruises on the head, arms and hands.
An unnatural interest in the status of the investigation and a compulsive need to talk about the case.
Suddenly shaving a beard or head hair, or growing facial hair.
Stopping the use of a personal vehicle for no obvious reason, putting it a garage or under a tarp, selling it or giving it away.
An increase or decrease in religious beliefs.
An increase in the use of alcohol or cigarettes.
Police say they've checked out nearly all of the more than 90 sex offenders living within a 3-mile radius of Somer's home. Repeated searches of a vacant house near where the little girl disappeared have not yet yielded any obvious clues.
Police are hoping that samples taken from the house and the landfill where Somer's body was found will give investigators something to go on.
A preliminary autopsy has been completed, but the results have not been released.
A group called Justice Coalition has put up a $30,000 reward for information leading to the arrest and conviction of Somer's killer. Some of that reward money came from Crimestoppers, which urged anyone with information to call 866-845-TIPS. Callers can remain anonymous.
Clay County police asked tipsters to call 877-227-6911.