Left or right handed.

[RivkahChaya]

I'm right handed, left hand dominant, left eye dominant. So, if I did these killings what would that mean?

I mentioned eye dominance upthread. In the military they check you for eye dominance, and tell you to try shooting your rifle according to eye dominance. In my basic training platoon, about half of the left-handed people fired right, and about 10% of the right-handed people fired left.

Muscle memory dictates that at this point in my life, batting lefty would not go well, but there is nothing inherent saying I can't do it. Fine skills like writing, crochet, tracery, carving I do with my right hand. It's my control hand.

"Muscle memory" isn't a literal thing, BTW, in case some people understand you as saying that muscle cells literally remember how to do something.

Any new physical task you learn is processed in your motor cortex. After practice, the processing is done in some other part of the brain, usually the part responsible for storing long-term memories, although if it's something like how to move your lips and tongue when you talk, that is processed in the language centers. Deaf people who have signed all their lives (and hearing children of Deaf parents) process the movements of their native sign language in the language areas of the brain. Children learning to write process forming letters in the motor cortex, but after time, people who write a lot move the processing to their language area. Commercial artists process drawing in the occipital lobe (where visual processing is done), and not in the motor cortex.

[The Good Michael]

There is a third, and technically more accurate answer than right or left.

The truth is, very little in any of these six murders indicates handedness which we interpret to mean the hand that someone writes with. A person who writes with their right hand is termed right handed, even if they do nothing else with this hand. Nor is hand dominance really an issue. The hand you use the most is the hand you use the most. The only way hand dominance comes into play is that it is the hand you protect. If someone throws their hands up to ward off a blow, typically arm crossed in front of the face, the hand on the bottom is the dominant hand. It's the one you reflexively don't want injured. It doesn't indicate a weakness in the other hand. And hand dominance is linked to eye dominance.

I'm right handed, left hand dominant, left eye dominant. So, if I did these killings what would that mean? Well, not a lot. If I came up behind someone and cut their throat, I would hold the knife in my left hand. I could just as successfully do it holding the knife in my right hand, I would just choose my left. Making the abdominal cuts, I would primarily use my right hand. Cutting out a uterus I would use my right hand, facial mutilations is a toss up, but I'd probably go with my right. Cutting an apron piece off would be my left hand.

Why would I switch up? Most people do. They just don't think about it. Barring true ambidexterity, people generally have a strength hand and a fine hand. And then they have the eye dominance. Things like batting, swinging, etc. don't have to do with hand dominance. It has to do with eye dominance. I see much better out of my left eye. So I bat righty. Muscle memory dictates that at this point in my life, batting lefty would not go well, but there is nothing inherent saying I can't do it. Fine skills like writing, crochet, tracery, carving I do with my right hand. It's my control hand. I hammer with my left, bang on doors with my left, and typically steer with my left, because it's my stronger hand.

In this case everything is determined by circumstance. Some things require certain motions in order to be effective. If those motions are not included with the hand that you would ordinarily use, you switch hands pretty unconsciously. For example. Cutting someone's throat, whether from the front or the back requires you to draw the knife cross body. So if you are facing someone, you use the hand that is on the other side of your body, put the knife across your body, and then draw towards you, pulling that hand back to it's own side of the body. If that makes sense. If Mary Kelly's killer was facing her on her left side, even if he was left handed, he used his right hand to accommodate that drawing motion. That motion is what is required for that to be successful. Not whether or not the knife is in the dominant hand. So that's actually a terrible cut to try and decide handedness.

Not that it matters, because if it was a smallish knife that was tough to use, a dull knife, or a knife with a large handle he would have used both hands. Which blows directionality completely. And not that it matters, because most knives are right hand knives. It's a subtle difference, but a lefty using a righty knife has the blade sharpened on the wrong side, and the handle is shaped backward. And some lefties I know use their right hand for a knife because they can't settle it properly in their left. And not that it matters, because he could be right handed but used used his left because his right arm was weaker. And it doesn't matter because most people would have shifted the hand they used so many times during the course of a murder like this that there is probably evidence enough to point to either hand equally.

And not that it matters, because there is no way you can use a knife bigger than a scalpel in a way that indicates with which hand you write, so if they were hoping to see some guy signing a document and have a big Perry Mason moment, they were going to be sorely disappointed. All they can hope to determine is what hand the killer was holding the knife in.

You spent a lot of time to say what I already said.

Mike

[Errata]

You spent a lot of time to say what I already said.

Mike

Maybe... But I managed to work in the phrase "Perry Mason moment", whereas you, sadly, did not.

Actually I expounded not because of the handedness issue, but because of how body motion often dictates which hand we use, not which hand we are more comfortable with. With all of the things in these murders that require cross draws, stabilizing hands, two hands, control vs. strength in order to keep from stabbing himself in the gut with his own knife, etc. that the knife probably spent an equal amount of time in each hand. For a reason. So any right handed person who thinks they would have had the knife in their right hand to commit a murder hasn't considered all the variables dictated by their own bodies. Never mind the crime scene.

[RivkahChaya]

So any right handed person who thinks they would have had the knife in their right hand to commit a murder hasn't considered all the variables dictated by their own bodies. Never mind the crime scene.

I'm not sure you are correct. Some right-handed people are very right-handed, for lack of a better expression, in a way that no left-handed person I have ever met is comparably left-handed. It may be the fact that so many more people are right-handed, my pool of left-handers is smaller, but it also might have something to do with the fact that some right-handed people have a gene for the trait, and a few people even have two genes. I have to leave soon, so I haven't worked out approximately what percentage of the population would have two genes, and at any rate, I do not know of any research that compares the left hand dexterity of right-handed people with one gene vs. right-handed people with two genes, so there may be a difference, or there may not be.

I just know that I consider myself right-handed, but I can use my left hand fairly well, and there have been a few times an unusual physical spot has required someone to use a left hand; when no actual left-handers have been present, it falls to me, because the other right-handers say they are hopeless at left-handed tasks.

I suspect I do not have the gene, tough, because the number of left-handed people in my family, and at any rate, I can confirm that I have at most, one, because my son is left-handed.

If you are left-handed, or truly ambidextrous, you might not realize how difficult left-handed tasks are for some right-handers.

Maybe... But I managed to work in the phrase "Perry Mason moment", whereas you, sadly, did not.

Did you ever wonder how Hamilton Burger kept getting re-elected? Or did he win every other case he ever had, and never lose to anyone but Mason? Really, by season three, you'd think he'd have learned "Uh-oh-- Mason's his attorney. Better offer a very attractive plea-bargain."

[Errata]

I'm not sure you are correct. Some right-handed people are very right-handed, for lack of a better expression, in a way that no left-handed person I have ever met is comparably left-handed.

This is true. There are extreme righties. My uncle is a neuropsychologist, so this stuff gets bandied about a lot at the holidays. Anyway, he says that the extreme tendency towards one hand goes with one of two things. A long time in early childhood where the hand was unusable. Longer than broken in a cast, but not necessarily permanently damaged. A year or so with a nonfunctioning left hand while developing fine motor skills retards the development of that hand. The other thing that goes with it is a less developed corpus collosum. And on a related note and not, dyslexia. Left handed people and ambidextrous people have a significantly larger corpus collosum. Of course, he's looking at the psychology and not the genetic or biology, but either way it is pretty rare.

Most people we know who seem useless with their other hand actually aren't. They have performance anxiety when asked to do something they think they can't do. Like write with their left hand. If you observe them doing a complex series of tasks without them being aware, they use their left the same amount as every other righty. Often if you ask someone to pay attention to some body function or movement that is usually subconscious... it's like Schroedinger. The act of observing disturbs the observed. It's like having to think about it makes them completely lose the ability to do it. Which absolutely happens to me if I have to coordinate my hands and feet. Which since I drive I can clearly do, just not on command, evidently.

But back to the subject, extreme handedness in a crime scene such as Mary Kelly would leave evidence in the extreme measures the killer would have to take in order to compensate for essentially having only one hand. Like shoving the bed to the other side of the room, hauling the body to one side of the bed or the other, extremely slanted knife wounds. The absence of compensatory behavior strongly suggests there wasn't extreme handedness.

[RivkahChaya]

Pretty much just in response to Errata, but anyone can read:

I hadn't thought about the corpus callosum; one of the theories behind the greater number of boys over girls in LD classes, which is to say, they are not retarded, but have specific learning disorders, is that one of the differences between male and female brains (ON THE WHOLE*) is that young male brains tend toward greater differentiation (or, less plasticity in infancy and childhood), and have proportionately smaller corpora callosa. That means that boys will have more trouble recovering from very minor assaults to the brain, and more difficulty in tasks in lab settings, such as having information fed to only one side of the brain, and then performing a task based on that information with the hand controlled by the opposite side. When you think about that, it means that boys with very specific sorts of deficits, like being deaf in only one ear, would be at a greater disadvantage than girls with the same disability.

At least, that info was current as of about 10 years ago, which was the last time I did much in-depth reading. I browse journal title pages from time to time, though, and I would have noticed something extraordinary, and contradictory, I think.

*When you compare groups of male brains vs. groups of female brains, the differences show up. That does not mean you cannot select one particular male brain to compare to one female brain, where the particular male brain has a larger corpus callosum, and the particular female brain is more highly differentiated. Also, while men's brains are on the whole, larger, they are in proportion to men's larger body size, and when you look at brains as a percentage of total body mass, women come out just slightly ahead. It's because men's brains have a little more structural tissue, which doesn't weigh as much. I'm not sure what would happen if you looked only at brains of humans who were 6 feet tall, whether they were men or women. It might be the difference in mass would go away, but I'm pretty sure the slightly larger corpus callosum would remain.

[RivkahChaya]

Errata:

Here's some approximate math.

Starting with the stat that about 80% of the population has the R (right-hand) gene, and just one copy is necessary to be right-handed, along with
the stats that about 10% of the population is left-handed, and that people with no copy of the R gene (00), then switching from 10ths to quarters, because it's easier to look at inheritance populations that way, I came up with this:

A little over 1/4th, or about 27% (22 out of 80) people don't have the gene (00), half of whom are right-handed, and half of whom are left-handed (about 14% of the total 80).

Of the people with the gene, 22 people have 2 copies (RR), and 36 people have one copy (0R/R0). All those people are also right-handed.

This assumes that being (RR) is not a problem, that would cause a pregnancy to spontaneously abort, or a child to exhibit a great degree of disability, but I strongly doubt those things, as that seems to be a pretty serious disadvantage compared to the small evolutionary advantage of handedness (it shortens learning time by causing people to "automatically" use the same hand all the time when learning a new task)*.

I do not know whether Right-handed people who are (00), (R0/0R) or (RR) have greater degrees of dominance, though, but I would love to see someone research that. It has practical implications now that we can do really amazing sorts of reconstructive surgeries on hands, but that are not without risks, and sometimes involve moving a toe, or a finger from the non-dominant hand. If we knew a child's genetic propensity to re-learn to do tasks with the other hand, if the dominant hand was severely injured, people could make better-informed decisions about haw much risk to take, and how much trauma of surgery to subject a child to.

*Most mammals demonstrate dominance, although some species show no tendency to be righties or lefties, as a species, while others show a tendency toward right or left, but not to the degree that humans seem to be right-handed as a whole. Cats that show a preference are left-pawed about 2 out of three times, but a significant number (I think it's about one in six) don't show a preference.

[Barnaby]

The mistake people make is to think that they were spooning and then he casually reached around her and did it.
Mike

Is that a knife in your pocket or are you just happy to see me?

[RivkahChaya]

Both.


characters

[Errata]

Is that a knife in your pocket or are you just happy to see me?

That's a thought. If she was down to her skivvies, certainly there had been some... preliminaries. Where the hell did he keep the knife? Because Kelly was killed with a not insignificant blade. Not really a pocket piece.

[RivkahChaya]

That's a thought. If she was down to her skivvies, certainly there had been some... preliminaries. Where the hell did he keep the knife? Because Kelly was killed with a not insignificant blade. Not really a pocket piece.

People carried knives then, though. Even up through the mid-20th century, people carried small knives. My father, who was a college professor, carried a folding pocket knife, and I knew a lot of men who still carried Boy Scout knives. My junior high school even had a rule that if you brought a knife to school (other than in your lunch), it could only be a folding pocket knife, shorter than something pretty short, but the rule specifically banned switchblades, while allowing Official Boy Scouts of America knives.

In schools in the US now, I don't even think you can bring a butter knife in your lunch, unless it's plastic.

I was a little kid, so I don't remember why, but I do remember that my father did use his on occasion, and not for nefarious purposes. Sometimes he used it as a screw driver, or to pry things. I think it was more a matter of no one seeing anything wrong with carrying knives, so people did.

But, at any rate, ankle sheathes. I know a lot of people who have those. Almost everyone I know who does a lot of hiking or camping has one. Those probably existed in 1888, and even if they were uncommon, I don't think you'd have to be a genius to come up with the idea independently.

[Michael W Richards]

Maybe... But I managed to work in the phrase "Perry Mason moment", whereas you, sadly, did not.

Actually I expounded not because of the handedness issue, but because of how body motion often dictates which hand we use, not which hand we are more comfortable with. With all of the things in these murders that require cross draws, stabilizing hands, two hands, control vs. strength in order to keep from stabbing himself in the gut with his own knife, etc. that the knife probably spent an equal amount of time in each hand. For a reason. So any right handed person who thinks they would have had the knife in their right hand to commit a murder hasn't considered all the variables dictated by their own bodies. Never mind the crime scene.

I wonder if that part in bold was accidental?

You bring up a good point that in fact helps my case Errata, the circumstances, the physicality required by the unique arrangements of the victims on the ground, or on the bed, can assist us if we can accurately recreate or reproduce the actions required to accomplish what we have to use as crime scene evidence.

Its not enough to assume motions,... specify. In my case I would love to see a specific series of actions suggested that would allow a right handed killer to access the right side of the throat of a woman who is lying on her right side, facing away, and is in a horizontal position while I am in a vertical one.

Best regards

[Errata]

I wonder if that part in bold was accidental?

You bring up a good point that in fact helps my case Errata, the circumstances, the physicality required by the unique arrangements of the victims on the ground, or on the bed, can assist us if we can accurately recreate or reproduce the actions required to accomplish what we have to use as crime scene evidence.

Its not enough to assume motions,... specify. In my case I would love to see a specific series of actions suggested that would allow a right handed killer to access the right side of the throat of a woman who is lying on her right side, facing away, and is in a horizontal position while I am in a vertical one.

Best regards

Ok. Give me a minute, I'm bringing in my trusty assistant. (who has had his throat cut quite a few times at this point.) I'm a big fan of trying things out.

We have a couple of options it seems. And a lot of it depends on positioning and the familiarity with the knife as a combat tool. First, let us discuss the victim on her side. This totally depends on whether she is asleep, or merely lying on her side. People who sleep on their side don't really do any such thing. They tend to be at a 45 degree angle to the mattress, as opposed to the 90 degree angle you would have if you were on your side on the floor playing monopoly or whatever. If she is sleeping the way described above, and has her head on the pillow, the simple fact is right or left handed, you don't get the right side of the neck at all. You have to turn her, at least a little. The point in the neck you are trying to get to is facing the mattress. The other way people sleep on their sides is that they are in fetal position from the waist down, but their torso is canted upright, almost on their back. In that case the right side of the neck is as exposed as it would be were she flat on her back.

As long as the proper point of the neck is exposed, it can be cut with either hand. For me, the easiest way is to reverse my grip on the knife, so the blade is coming out pinky side and not thumb side. The mechanics involved are not terribly different that using a sickle. You bring the blade down so it goes behind the ear, and then yank forward. If I were using my left hand, it's a little harder, because when you pull a knife towards you, you pull it towards the shoulder of the hand you are using. So left handed, standing below the head facing her back isn't going to work because you have to fight to maintain contact with the throat. You either have to move above her head and face the other way, or get lower by about two feet. Obviously the first choice is easier, but the second choice can be accomplished merely by sitting on the bed. So it depends on how wed you are to the idea that he was standing. Or he could use both hands which will straighten out the cutting track.

The real question is, where do you put your other hand? And this does relate to the above. If he is standing and she is lying on a bed, and kind of on the opposite side of the bed, then he is making a quick sharp jerking movement while bent over at a significant angle. And we assume he wants neither to fall into the corpse not back on his rump. So he has to steady himself with the other hand. The bed seems like the obvious choice, but if she is sleeping (as opposed to passed out where none of this applies) that's a significant motion that could disturb her. Especially since he would be planting most of weight like, and inch away from her on a crap mattress. It would cause her to roll towards his hand. The best way to stabilize both himself and his victim would to grab her left shoulder and press down on it, rolling her head towards him exposing the throat, and keeping his balance. But she would absolutely wake up to that. The only way he doesn't risk waking her is by throwing himself way over balance by planting a hand on the opposite wall. Making using the left hand impossible, and the right pretty tricky. If he's a lefty he can steady himself on the headboard.

If she wasn't asleep and was just lying on her side, there's no reason not to reposition her to a more convenient posture. Lefty or righty, it would be best if she was flat on her back. So he pulls her shoulder towards him so she shifts to her back, and then he cuts her throat. If she's passed out drunk, he could twirl her over his head and cut her throat while she was in a headstand and she wouldn't make a peep. So I reject the notion that she was passed out, simply because there is no reason to leave her in such an inconvenient position.

People do automatically adjust for this stuff if possible. It's why we turn a piece of paper 30 degrees when we start to write on it (at least with our alphabet. People who write Hebrew turn it the other way, no matter what hand they write with). So I don't see him sitting there going "Gee, Maybe I should move towards the door, no, wait, maybe facing the foot of the bed.. no.." He took whatever steps he needed to take to adjust, assuming they were available to him.

I would do it righty because I wouldn't want to move towards a wall and get myself crowded in. I'm also more comfortable with a reverse grip than a standard one, for which I get teased mercilessly. And this is something I could do with either hand. But if I had to essentially stand against the wall to be in position to cut her throat, I'd do it lefty since I'm not going to fight the wall for elbow room. Personally, I wouldn't care about waking her, because I'm confident of my ability to conceal the knife in my hand until it comes up for the blow, which means she won't have time to scream. Assuming I care if she screams.

But no matter which hand I use, how I steady myself, what state the victim is in, the easiest thing to do if she is even a little turned away from me is to stab her in the side of the throat that is closest. I might make along cut later, but that is by far the easiest way to dispatch her. Doing anything else is either ignorance or compulsion. If someone thinks they have to cut the throat from ear to ear to kill someone, or someone who has to slice across the throat or the become desperately uncomfortable and feel just wrong. Why make your job harder, you know? The problem is, the two hardest types of people to pin down are the stupid and the mad. And if he's stupid or OCD, he may do ridiculous things that make no sense for reasons we may never understand. At which point, I got nothing. For all I know he did it from under the bed while singing arias from Rigoletto.

[Errata]

People carried knives then, though. Even up through the mid-20th century, people carried small knives. My father, who was a college professor, carried a folding pocket knife, and I knew a lot of men who still carried Boy Scout knives. My junior high school even had a rule that if you brought a knife to school (other than in your lunch), it could only be a folding pocket knife, shorter than something pretty short, but the rule specifically banned switchblades, while allowing Official Boy Scouts of America knives.

In schools in the US now, I don't even think you can bring a butter knife in your lunch, unless it's plastic.

I was a little kid, so I don't remember why, but I do remember that my father did use his on occasion, and not for nefarious purposes. Sometimes he used it as a screw driver, or to pry things. I think it was more a matter of no one seeing anything wrong with carrying knives, so people did.

But, at any rate, ankle sheathes. I know a lot of people who have those. Almost everyone I know who does a lot of hiking or camping has one. Those probably existed in 1888, and even if they were uncommon, I don't think you'd have to be a genius to come up with the idea independently.

Well, an ankle sheath only works with a blade so long, and that depends on the wearier. I wore one during Living Chess Match for a coup de grace during my second fight, and I thought I was so smart but it was a 14 inch dull hunk of steel strapped to my ankle working as a very effective splint, and rubbing the skin off my ankle.

I think one of the blades used on Kelly was more than five inches long, probably six or seven. Which seems fine until you add a three inch hilt, and now you have an 8-10 inch blade, which just does not go in a boot well. Back of the pants seems to be the murder weapon storage of choice, but she'd feel it. As she would if it were on his belt or his side.

To me, it means that she didn't think anything of the knife. It did not trigger "Possible Jack The Ripper" in her mind. So she knew him maybe, or the knife was common to the man's profession. A sailors knife, a military dagger, maybe even tailor shears.

Or he had it in a bag or box. Which presents it's own problems, like how do you pull it out of a bag without her noticing. Because despite the fact they are inside, there are a lot of things he can't count on that evidently he is counting on. He can't count on her falling asleep within his timeline. Not something he has cared about previously. Which I think is telling. He doesn't know how much time he has, but evidently he is counting on having a couple of hours. And he can't keep her in the room without the knife. If she wants to go back out for more drinks, he can't stop her without seriously alarming her, and possibly leading to her escape if he can't get to his knife in a timely fashion. He doesn't have control over her without the knife. So I can't see him putting it elsewhere.

I dunno. It's one of the reasons it makes me think That Mary Kelly wasn't killed by Jack. Too many changes.

[Steve S]

The whole idea of knife carry is an interesting one..with safety,concealment and ease of access all playing a part....Not propounding as answers,but I reckon either a right leg "truncheon pocket" set-up or a left forearm sheath would work...If he was that organised! ...(reverse if left-handed...)