Agree. I believe that the grip used with this knife (regardless of who did it) was not the one shown in Psycho, but the one shown in training videos for this very knife (of which there are many on youtube).
The weapon is designed for careful placement, rapid death, and silence. If this killing had been frenzied, there'd have been more bloody footprints. The killer planned to kill people who were lying down (and with himself positioned in a manner so as to avoid as much arterial blood spurt as possible - which was also aided by some of the victims still being in bed or under covers).
I can easily imagine a killer who had taken criminal forensics (even at the basic level) to use a method in which the initial wound (designed to silence but lethal in and of itself) was placed in one manner, and then the body pushed into a position where it would not bleed out on the perp. Sure, the murderer got victim blood on himself, but didn't cut himself and leave a trail of blood nor even leave blood glove prints or foot prints everywhere. Just a few footprints that we know of.
IMO.
It's also a place where frustration biters bite themselves.
I now feel officially weird for having known this and for having actually seen it (in mental hospitals). I'm sure it must happen in jails as well. NIMH calls it "anger biting," I think.
Based upon the paralogical reasoning of the anger-impulsive biter, this paper addresses the overload of emotional catharsis which can block a full memory of the biting event and suspend the logical infrastructure of rational behavior. In an effort to overcome these types of investigative...
pubmed.ncbi.nlm.nih.gov
Biting behaviors aren't well-studied (people self-bite; other-bite and it often starts in childhood).
One of the treatments for it is to advise the biter to "self-talk" and calm themselves down. There are ton of experiments on non-human primates (and on some rodents). Turns out being locked up in a small cage with little to do increases the amount of self-biting in those species.
Hmmm. Apparently seen in adolescent in-patient wards as well. In the animal studies, they were able to take samples of spinal and brain fluid (too invasive for humans) and found that the biting did reset and improve the dopamine processes (calming processes) in the brain.
IMO. Though there are links above, I'm obviously speculating.