Only 27% of 6-Year Olds Killed by Strangers. Of 644 U.S. homicides of victims age 6 (between 1976-2004), 73% knew the offender and 27% of the killers were strangers, according to Bureau of Justice statistics.
Most Very Young Children Killed by Parents. Of 769 U.S. homicides of victims under age 5 in 1996, 50.2% were killed by parents, 6% by other family members, 29.8% by friends/acquaintances, and 2.4% by strangers, according to Bureau of Justice statistics. Unfortunately, no equivalent break-down is provided for children age 6. The lion's share of these "infanticides" are under age 1 and the number declines steadily for each year of age.
Specific Evidence
RN refers to John by name.
RN very "personal" in remarks directed at John.
Ransom amount may be related to size of John's Salary Bonus; if true, this suggests "insider" information.
Evidence Perp Did Not Know Family
RN does not refer to JBR by name
Any "personal" information, including John's Salary Bonus amount, in theory, could have been obtained even by a stranger intruder if they spent several hours in the house while Ramseys at Xmas party.
How Old Was the Perp?
Evidence for a Young Perp
Numerous movie references in RN
Victim age indicates younger, inexperienced perpetrator. Younger victims are easier to control and overpower.