I have always had a problem thinking of an intruder, who wasn't known to the child, committing this murder. I considered Elizabeth,however, her sister saw the intruder,then Polly whose intruder was hardly stealth, the other girls witnessed her abduction, and Danielle, which was the oddest of all. Westerfield, who was balding, had a mustache, and was drunk, managed to slip into the house while parents were home, climb those stairs, quietly remove her, not waking her parents or brothers,even the dog wasn't alarmed, and yet, not a fiber, not a hair, not a fingerprint of his was found in that house. Is this not amazing!! Of course Westerfield didn't leave a ransom note, because likely an adult who commits this type of crime has no reason to leave one,not when his only motive is murderous lust. What kind of person needs to leave a ransom note? A person who fantasizes about kidnapping? A person who didn't admit to himself that he was going to kill her? ....and why is that note so personal, asking for John's bonus, mentioning his business, showing his hate for "fatcats", clearly saying, I took her, I killed her, because you have it all and you didn't share.
It sounds like tiny tims father ,given a temper and a sociopathic personality could have "dunnit" as retribution for the injustices, or tiny tim himself protected by his parent who "understands".