Seriously!!
I don't know if this is factual but I'd be very surprised if any nine yr old who committed a murder has ever actually successfully covered it up and managed to fool the authorities for any real length of time. I think that's probably impossible.
And why do so few people consider that if there was an intruder they were likely waiting in the house while the Ramseys were out for the evening which would make a lot of sense and also explain why the note is so dang long - they were restless and kind of spinning out from sitting around waiting.
Okay, can you unpack your intruder did it theory?
Was it an intruder known to the Rs or a random stranger?
How did they travel to and from the R home?
I will set aside how did they enter and exit for now.
Was the intruder there to kidnap JBR? Or to murder her? Or to SA her?
If there to SA, why bother with the RN, especially if leaving the body behind?
If there to murder her, why leave a RN?
If there to kidnap her, why not get the heck out of there once JBR was taken from her bedroom?
What did the intruder come prepared with? The RN was written on PR’s notepad with her pen. The SA was with PR’s art supplies.
I’ll set aside the “fed pineapple” for now.
I don’t buy the RN being dramatic and long due to spinning out. Who spins out into stealing lines from Dirty Harry movies? Or utter ridiculousness - “we are a foreign faction”. A true RN would be short and to the point - I have your daughter. Wait for my call. $118,000. No police or I kill her”
Why leave the body behind but also leave the RN behind?
IMO, an intruder would be there for one purpose - pick one.
Kidnap? Leave short note and take JBR with you when you leave. No need for SA, murder, garrotté etc.
SA? Commit the act then leave. No RN required.
Murder? Commit the act then leave. No SA or RN required.
All imo