Thursday, April 19, 2012

The Case of Preston Hughes III: Shandra's Neck

This is Shandra's neck.

This is the knife the police found in Preston Hughes' closet.

In this post, I am going to stick that knife in a generic neck having a wound similar to Shandra's. I'm going to do that so we can better understand the case of Preston Hughes III. Before I do, however, we need to understand a little bit about necks in general and Shandra Charles' neck in particular. We also need to know something about the wound and the knife. Let's get to it.

Necks in General
I present a cross-section of a human neck. Though it makes no difference, you can presume you are looking from the top down.

The pair of red and blue ovals on either side of the centerline are the (common) carotid arteries and the (internal) jugular veins. According to the trial testimony, the left carotid and jugular were perforated / severed. You can see that it would be difficult to sever the carotid without also severing the jugular.

The yellow/orange and light blue portions near the middle of the neck constitute one of the cervical vertebrae. I provide a separate image of the vertebrae below.

When I stick Preston's knife into the generic neck, I will assume that I can't penetrate the vertebrae. The knife blade will have to pass in front of the vertebrae or along its left side.

Referring once again to the original cross section of the neck, the large red ellipse located towards the front center is the esophagus. Food and drink (normally) travel down the esophagus to the stomach.

The white area forward of the esophagus is the pathway through the larynx. The larynx surrounds and controls that pathway. The cream colored arch forward of the larynx pathway is the thyroid cartilage. The thyroid cartilage is pretty stiff, which is a good thing since I was once hit in the throat with a record-setting line-drive softball that dropped me like a sack of Idaho russets.

But I digress.

The back of the larynx is less well protected, based on the entirely reasonable assumption that softballs to the front of the throat will be more common than knives to the back of the throat. I want to point out, however, that softballs are not all that soft.

But I digress.

Shandra's Neck
So that we can scale everything properly, we need to know the circumference of Shandra's neck. It turns out we can get a good estimate if we know her body mass index (BMI), and we can calculate Shandra's body mass index if I know her height and weight. The not-so-helpful fill-in medical examiner ME actually testified to her height and weight. (Will wonders never cease?) If you'll give me a moment to myself, I'll calculate Shandra's BMI.

(She was 65 inches tall. That's 1.65 meters. She weighed 127 pounds. That's 58 kilograms. Now I need to divide the weight in kilograms by the square of the height in meters. Lemme see. That's 58 divided by 1.65 then divided by 1.65 again. That's 21.30395. Got it.)

Shandra had a BMI of 21. That indicates that she was quite lean. From Wikipedia:
... a BMI of 18.5 to 25 may indicate optimal weight; a BMI lower than 18.5 suggests the person is underweight while a number above 25 may indicate the person is overweight; ... a number above 30 suggests the person is obese ...
Here's where it gets good, assuming you're a complete geek. Some clever researchers have found that one can estimate the body mass index from the neck circumference. I want to do the reverse. I want to estimate Shandra's neck circumference from her BMI. I'll therefore rely on a plot those clever researchers very kindly presented in their paper. The plot shows the actual neck circumferences for the females in their study plotted against the BMI values.

Based on that plot, Shandra's neck circumference was no greater than 34 centimeters. It was more likely 32 centimeters, or thereabouts. That's 13 inches all the way around, or 6.5 inches half way around. In the figure below, I've added a series of 1/4" bars along the left side of the neck. There are 26 of those 1/4" bars, as there should be if they are to add up to 6.5 inches. These 1/4" bars will make it much easier to see what is going on.

The Wound
We learn a little bit about the neck wound from the not-so-informative, last-minute, fill-in medical examiner.
Q. Doctor, moving along to the autopsy report, prepared on the body of the young woman in this case, Shandra Charles, having reviewed that report, do you have a medical opinion as to the cause of death of Shandra Charles? 
A. Yes, sir. 
Q. What is that? 
A. LaShandra Charles died as a result of a stab wound to the neck. 
Q. Could you describe more specifically that stab wound to the neck? 
A. Yes, sir. There was a stab wound to the left side of the neck located 2 inches to the left of the midline and 8 inches below the top of the head. The instrument perforated the left jugular vein and the left common carotid artery, two of the large vessels in the neck. 
Q. Is this injury similar to the injury that the child, Marcell Taylor, received? 
A. That is correct. 
Q. In fact, the arteries and veins were severed the same as on the child, Marcell Taylor? 
A. That is correct.
That's it as far as the neck wound goes. Seriously. That's it.

As far as this post is concerned, the take away from that enlightening testimony is that the wound was located 2 inches from the front of the neck. I assume the measurement was to the center of the wound.

We'll have to look elsewhere for the width of the wound. For that, I turn to the police report of Officer J.L. Waltmon. He's the one who met the ambulance carrying Shandra as it arrived at Ben Taub Hospital. I present the relevant passage below. Forgive the grammar and punctuation, for he knows not what he does.
Sgt. then view the comps. body and found that she had a stab wound to the left side of the neck. This wound was 1 1/2" wide and 1 3/4" down from the left ear lobe on the left side of the neck.
Ignore the trauma to the English language, if you would, and note instead that Waltmon claims the neck wound was 1.5 inches wide.

Now, I'll shade 6 of those 1/4" bars to represent the 1.5" wound. Then I'll center the wound at a point 2 inches from the front of the neck. That's right between the eighth and ninth of the 1/4" bars. Here you go.

The Knife
We'll be discussing the knife in more detail in future posts. For know we just want to know its dimensions. Let's turn to the ever-informative, fill-in medical examiner for an in-depth discussion.
Q. Doctor, let me show you what has been marked and offered into evidence and admitted into evidence as State's Exhibit No. 20. Would you please examine that knife? I'll give you a yardstick. Would you measure the blade on the knife for me please. 
A. State's Exhiblt 20 is what is classified as a sharp instrument, a hunting knife, with a blade that measures a little more than 5 1/4 inches in length with a width of slightly more than an inch.
While I can't confirm the measurements from the image, I can confirm that the ratio of blade length to blade width is pretty much as testified. If the blade length is indeed 5 1/4 inches in length, then the blade width is close to 1 inch, though the width varies along the blade.

The Criteria
Not just any knife in the neck will do. I have inserted the knife into the neck in 22 different fashions, in 15 degree increments, with the sharp edge pointing in each direction. Only the front-to-back and the side-to-side stabbings are possible reasonable recreations of what happened to Shandra. All other stabbings, those in between a side-to-side and a front-to-back stabbing, are unreasonable.

I decided which of the stabbings are reasonable and which are unreasonable based on the following criteria.
1. The knife must cut through, partially or completely, the left common carotid artery and the left interior jugular vein. 
2. The knife must not cut through the right carotid artery. If Shandra had both carotids severed, she would have died almost instantaneously. 
3. The knife cannot penetrate the cervical vertebrae. 
4. The knife must be inserted forcefully. In other words, the wound must be deep unless it hits the cervical vertebrae. Every other stab wound was forceful. Marcell's neck wound was through-and-through. Marcell's chest wound was also through-and-through, penetrating his shoulder blade in the process. Shandra's chest wound was 4 1/2 inches deep. 
5. The entry wound must be centered about a point two inches from the front of the neck, or nearly so. 
6. The entry wound must be 1.5 inches wide, or nearly so.
Marcell's neck wound was a through-and-through neck wound, nominally front-to-rear, directed slightly from right to left. According to the testimony presented above, Shandra's neck injury was similar to Marcell's neck injury, at least in terms of severing both a carotid and a jugular. We'll therefore look first at a front-to-back wound, traveling slightly right to left.

This stabbing almost works. When the knife just barely nicks the carotid, the wound is a bit too far forward. If the knife is moved to more seriously cut the carotid, the wound is even further forward. If Shandra's neck wound was more closely centered about a point 1.5 inches from the front of the neck, instead of 2 inches, then this path would be a possibly reasonable recreation.

Here's another path, this time directly from front to back.

This one also works, assuming the wound was centered somewhat further forward than specified in the testimony.

Finally in this category, a path travelling slightly from left to right.

This one doesn't work. The resulting neck wound is noticeably smaller than 1.5 inches wide.

In general, the front-to-rear recreations may be representative of what happened to Shandra. In general, the wound would have been located somewhat further forward than specified in the trial testimony.

Intermediate Angles
Stab angles at any angle near 45 degrees simply don't work. Consider the image below.

In these cases, the knife hits the vertebrae after severing the carotid and the jugular. The knife can't penetrate very far, and the entry wound is far less than 1.5 inches wide.

Side to Side
A side-to-side stabbing is also a reasonable possibility. Consider the following images.

In general, the side-to-side stabbings are reasonable possibilities. In each case, a forceful side-to-side stabbing would sever the trachea. Shandra would not have been able to speak to anyone.

General Observations
I was surprised the reasonable possibilities narrowed down to the extremes. It seems as if the knife in Shandra's neck must have traveled either from front to rear or from side to side. It's a shame that the jury was left uninformed as to which.

The autopsy reports should clarify the wound paths. I don't yet have a copy of the either report, but I've made an initial inquiry. I'll need to pursue the autopsy reports more aggressively.

Whether the knife traveled front-to-rear or side-to-side, the wound path challenges the State's case. I explain why in my next post in this series.

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