Left or right handed.

[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.

[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]

Both.


characters

[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]

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.

[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.

[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]

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]

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.

[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

[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.

[Errata]

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.

[Wickerman]

With that in mind, does anyone else think it's possible that JTR changed his MO to avoid getting blood on his clothes, or at least avoid the appearance of it, by wearing a black overcoat, or something?

I honestly do not think it would be necessary to wear a top coat to hide blood stains. The way we interpret the method of kill, and the direction of cuts, assuming we read this right, it seems to me the killer in a worst case might get blood on his cuffs, but nothing more than that.

With the Kelly murder, he could have rolled his sleeves up, but so long as there was no splashing of blood any spots he got on his clothes would be minimal. Out on the street at night no-one would detect small blood stains on dark clothing.

[The Good Michael]

I think what Michael W. Richards is suggesting is simply that the conditions of the room more easily reflect a left handed perpetrator.

No, what was said was that the killer was more likely left-handed because the conditions and situation of the victim as she was killed would have been difficult for a right-handed man. The fact is the handedness doesn't enter into what opportunity was presented. Therefore, the killer had the same chance as anyone else in society of being left-handed, period.

Mike

[GregBaron]

South paw logistics...

I think what Michael W. Richards is suggesting is simply that the conditions of the room more easily reflect a left handed perpetrator. Period. Can anyone say the killer was left handed, No. It appears the execution would be more cumbersome for a right hander. But this isn’t an engineering project and we’re obviously not dealing with a sane man. Perhaps he stripped naked and danced around the bed in all kinds of contorted positions as he went about his work, we simply don’t know…

If Mary was on her back, it would probably be easiest for a right hander to mount her and grab her head with his left while slashing with the right. I think this would get more blood on his person though and would leave more blood on the bed rather than pooling beneath. It does seem more likely that she was in the fetal position facing the wall when the perp pulled her slightly toward himself, maybe she briefly awoke and instinctively pulled the sheet over her face, and then the cut was made. This would be awkward for a right hander standing or kneeling above her left shoulder. Again, just speculation based on the conditions of the scene.

The only reason I think this discussion is of interest is because the killer(s) of Cs 1-4 was/were almost certainly right handed.

As I said before, I’d like to know in which hand Blotchy carried his beer……..?

Greg