Hi,
you caught me a little bit flat-footed here, since I have not much ideas about duck hunting. Didn't know for example, they use burlap to make blinds. However, I know my serial killers.
Basically, there are three different kinds of SKs out there, who dismember the bodies:
a.) as forensic counter-measure to prevent identification. This behavior is in fact relative common in mid- to low-organized sexual predator types. Berdella, partially Dahmer or also Rifkin (since we are at Long Island again) used it. Typically, those SKs dispose the bigger part of the body, often the whole shebang in the normal trash or spread them over a wide areas in places that are not so easy found. However, often they also keep a part for some time, either boiled down skulls (like Dahmer did) or by burying heads in their garden (like Berdella did). An SK, who uses dismembering as countermeasure has a good chance to become sloppy over time, after he got away with it several times and thus "changes" to methods with less effort. Rifkin is a good example for that. However, it's not really "evolving", it's just getting sloppy in the same way other SKs go sloppy when their spiral down beginns (compare Bundy for that).
b.) as souvenirs. Some keep body parts as souvenirs, mostly heads/skulls. While they get rid of the bigger part of the body, they keep the part that intrigues them. Again, Jeffrey Dahmer is an example, he kept some skulls to build the infamous altar. Since, for most of the body, this is only about forensic counter-measure and body disposal, there is always a possibility, that kind changes something in the disposal method or gets sloppy. That would mean, instead of body parts, one would suddenly for example find beheaded bodies.
c.) The Keepers. This is the rarest kind and I'm not sure, whether it's not even the rarest kind of all SK types. In this case, dismemberment doesn't serve as forensic counter-measure or means to dispose of bodies but is part of ritual and thereby of signature. Typical warning signs are
- torso or head staging in areas, the killer had to know they were found soon
- body parts of the same victim popping up in distant places over years
- body parts popping up when another SK makes headlines
It's important to understand, that this kind of SK doesn't dismember bodies to prevent identification. They do it because it's what they do, part of their fantasy that forms the signature. Thus, in a way, and especially in connection with the body part staging, those killers are much more similar to a Zodiac than a Jeffrey Dahmer. It's about attention and making statements. And because it's not about disposal (if they can, they keep as many body parts as possible in freezers, mummified or embalmed as possible and it's hard for them to put them out there to be found), they will NOT change this part of their signature unless they begin to spiral down.
Manorville is by all signs a Keeper-type. Jessica Taylor's torso was staged on top of a pile of wood along a path known by dog walkers. Her Hands and forearms, even her head, popped up not only years later but also only after another killer in the same area made headlines. Same with the Jane Dow. So, I fon't think, Manorville would evolve in a regular strangler and suddenly start to drop whole bodies somewhere. There wouldn't be any fun in it for him at all.
Now, that is my opinion and I don't claim to be always right (even I had a pretty good quota over the last few cases). So lets speculate a little about other reasons:
- A lot of SKs start with a victim that is from their social vicinity.
That is the reason, why the early victims are often key to blow the case open. So, theoretically, if there was some connection to the early victim, the killer would have seen a need for more effective counter-measures.
- Extreme sadists can in rare cases develop a taste for peri-mortem dismembering. Since the parts found were alreay years old, no ME would find tourniquet impressions anymore. So, theoretically, that's a possibility. However, a psychopath/sadist has a tendency to go at some point down the spiral and when he enters this phase, his killings become less elaborate, the signature disappears and it's all about primal instincts. So he would maybe change to less elaborate methods (but then, the kill/time quota for Gilgo is too slow for a psychopath in spiral down phase)
- If there are only a few victims dismembered, then a few burnt (for example), then a few painted green (only example to make it plakative) and whatever else, it could be a beginner still searching for himself. The urge to kill is already fully blown, but he is still experimenting to figure out, which method is the most "him".
- another possibility is, he is a dismemberer, but lost his infrastructure. dismembering worked fine because he had the privacy of his garage ... but then his house was foreclosed and now he has no space with the needed privacy.
So, theoretically, there are some possibilities.
A question about duck hunters: Would a duck hunter who drives a pickup or SUV have regularly burlap as sheets or sacks in his bed/trunk? Or only during a certain season? And when is duck season at LI?