And finally, the killer's ability to avoid police roadblocks and elude capture has also stirred the public imagination. Is he (or she, or they) planning his attacks carefully, or is he simply lucky?
The attention paid to profilers, who are experts trained to speculate about crimes, also increases the temptation to try it oneself.
"You can't be an amateur ballistics evidence expert," said Thompson. "You can become an amateur profiler by simply coming up with a theory."
Zodiac, JonBenét Captured Public Imagination, Too
The D.C.-area sniper case is not the first to spur the public to theorize about the attacker.
"We still get calls — almost daily — from people who believe they know who the Zodiac is," said San Francisco Police Department Inspector Kelly Carroll, referring to the so-called Zodiac Killer. The killer was responsible for at least six deaths in the San Francisco area in the late 1960s and early 1970s but he claimed in letters to police to have killed as many as 37 people.
Many people spent hours debating about the possible killer of JonBenét Ramsey, the 6-year-old girl found strangled in her Colorado home in 1996; the mysterious disappearance of former intern Chandra Levy, whose remains were found in a Washington, D.C., park; and the death of Britain's Princess Diana. The assassination of John F. Kennedy may have prompted the most armchair sleuthing.
Speculation over the current sniper has been heightened by the nonstop news coverage, says Thompson.
It may be harmful by distracting the public from other important stories, such as the possibility of war with Iraq, he says.
On the other hand, he admits, it might also aid in the capture of the killer.