I'm going to touch on a few topics & items, most that have been mentioned thus far, however I am going to be focusing in on a more detailed (ie. in-depth) analysis aspect in an attempt to provide some food for thought & feedback. All insights are "IMO", so yours may vary.
The 1992 David Chereck, age 15, strangulation case in Skokie & Morton Grove, IL:
I had known about this case. Not in full detail, but sufficient info to comment. Bob, you stated "Found within two blocks of his home in wooded area".
That part is not true. He was found actually more than a mile from his house, in a wooded area in the next suburb. He was also found in just a T-shirt, pants, & socks. His shoes and winter jacket were completely missing from the scene. Initially there was considerable speculation of auto-erotic asphyxia.
This case was hugely botched from the get-go, as it's jurisdiction was fought over by an incompetent local PD (a PD that severely botched handling the disappearance of my own sister in 1970), but fell in the hands of an even more highly incompetent county "Forest Preserve" police force.
My opinion: I find it highly unlikely the perp of that case (CA "suspect", or other) had anything to do with Bill's case, for the reasons:
1. Perp drove victim far from abduction site. Perp concealed body in dense wooded area, not in very public place & plain open view like Bill.
2. Perp also stripped David of his jacket and shoes, and took them from scene (never found items, afaik).
3. Perp highly unlikely to simply commit his act within 2 blocks of your home. Far more his MO (modus operandi) to disable Bill and drive far away to a very secluded place.
4. Several more reasons, but main ones already listed are significant enough.
The "Car" (in Bill's case):
Tho I never rule out anything (tho I may keep things below 5% probability), I do not see a vehicle being used, especially for the 3rd attack/death.
1. Use of a vehicle is far more "witness-able" and "cumbersome" in a virtually slightly over 1 block radius attack. (on abduction AND the very open final death scene).
2. Use of a vehicle largest "benefit" would be to carry Bill far from the abduction point. That did not occur, in the least.
3. Use of a vehicle is far more unlikely in "spur of the moment" chances of catching Bill away from family, in front of his own home.
4. Use of a vehicle would also allow Bill to easily/readily notice it either on approach, or parked nearby the house. Or upon exit of the "occupants".
These are my main reasons for placing the use of a vehicle as "unlikely".
Use of black plastic bag & inner tube (attack #1):
1. IMO, does not afford any justification or reason as to why Bill did not see his attackers. Even in situations attacked "from behind". Probably the best way I can demonstrate this is a real life recreation of the event. Since surprise would be a necessary key element, it's hard to recreate. However, hypothetically, if you were riding a bicycle and have two people jump out from a concealed area (say a tree/bush) behind you: First, unless you were riding a bike at a bare crawl (most kids don't), you would be a fair distance ahead of them by the time they jumped out. Most trees wouldn't afford 100% concealment for a very "close up" victim.
But mainly, in the act of anyone attempting to place a bag over your head, even by surprise, there is almost always ample time to react and see that person's face.
Simply put, I place myself in any victim's shoes. I'd feel comfortable challenging anyone to be able to do it successfully to me, and not have me see their face.
It's been asked "Why those two items? Why the need for the bag? Why not just the inner tube for strangulation?"
I'm not a doctor, medical examiner, nor killer, but will provide the following info from what I know.
1. Both items would be needed for maximum asphyxiation in the shortest amount of time, thus reducing "struggle/consciousness" time to a minimum.
2. Quite simply, the bag limits breathable air to virtually close to zero air. The inner tube (or any tying item) seals the enclosure and maintains the seal. It's rather scary just thinking about it, I know. Just trying to explain.
3. But this allows use of the victim's hands (unless they are held/tied) before the point of unconsciousness, to tear off the items
4. The note left said "He was warned". Keyword is "WAS". Not "is". If Bill didn't fake that note, then to me that significantly indicates they intended him NOT to walk away alive.
5. All of these are reasons why I said in my very first post that I believe the intent of #1 attack was to kill on that date, rather than scare. I also can't answer why they used an inner tube, rather than say rope or duct tape, other than 1. possibly handy for the perps to have. 2. Due to the stretchy material, it actually would be the best material to both seal and ADD/maintain compression pressure to the throat/neck once it is tied off.
I would appreciate feedback to see what others think, or if they disagree with certain parts, and opposing viewpoints, so we can exchange ideas, and reduce the chances of going in wrong directions.
Right now I'm reviewing aerial photos of the neighborhood taken in 1971. That is the "closest" year that is available for me at present, tho typically for a fee you can order a specific year, or one much closer to 1979. The ultimate goal is to get a 100% accurate detailed view of each scene and surroundings, as if standing right there. That would be very high value as a "foundation" in any successful investigation. That is why you often see LE standing silent at a scene, turning & taking in the entire 360° around them, in deep thought.
In my thinking, I literally have hundreds of vital questions about physical neighborhood details, scene details, details on your observations between & after each attack & I also still have comments/opinions on numerous segments ("evidence" at scene, etc). However, this post is already more lengthy than I originally intended, so i will end here for now.