What Your Bones Can Tell About You

Transcription

1 What Your Bones Can Tell About You The Postmortem Interval Determining the time of death A pathologist can easily determine the time of death when the body is recovered with in 24 hours of death by using specific indicators. After 24 hours have passed, the pathologist must investigate environmental condition and other factors at the scene, such as using forensic entomology. Algor mortis is one of the specific indicators used to aid in determining the time of death. It refers to the cooling rate of the body after death. Generally the body cools degrees Fahrenheit until it reaches the ambient temperature. Other factors observed also are type of clothing, if it is wet, type of air movement etc. Livor mortis or lividity refers to the pooling of blood after the heart stops caused by gravity. It begins with in a half an hour of death and is most obvious after 12 hours. Post 12 hours, the livor mortis evidence is permanent. The skin will appear to be purplish red where the blood has pooled and can indicate the position of the body at the time of death. (FYI: Livor mortis doesn t happen in areas of the body that actually touch the ground because the capillaries are constricted) Rigor mortis refers to the stiffness or rigidity of the skeletal muscles after death. (You have probably seen this on the side of the road with some animals that have their limbs stretched in the air) The muscles are relaxed at time of death; in the meantime, the ATP in the muscles break down, fluid concentrations change causing the muscles to become rigid. Rigor mortis begins in the smaller muscles first, and is typically seen first in the face, jaws and neck; relaxation happens in the same order in which it stiffened. The noticeable stiffness of the body occurs within two or three hours after death and is gone within approximately 30 hours leaving the body limp. Rigor mortis is also affected by the conditions of the environment and body, such as temperature, dehydration etc. Forensic Anthropology Anthropology is the study of humankind including anatomy, variability, evolution, and culture. Forensic anthropology is a type of applied physical anthropology that specializes in the human skeletal system and its changes and variations, for purposes of legal inquiry and ultimately for presentation in courts of law. Skeletal identification can be used in identifying a person because every human being s skeleton is unique in some ways. Genetics play a big part in the uniqueness of a skeleton, but also does injury, growth and use. A forensic anthropologist will look at the unique skeletal features and compare them to antemortem (before death) evidence. In this comparison, cause of death can sometimes be determined. Applications of modern forensic anthropology can be applied to cases that are hundreds or even thousands of years old. The primary task of a forensic anthropologist is to examine bodies that have decomposed, ones that were badly burned, been mummified, or skeletonized. The following questions should be kept mind when working on a case: Are the remains human? Are the remains of a single individual or mixed remains of several individuals? When did the death occur? ~Forensic Anthropology 1

2 Was the body disturbed after death? What are the gender, age, and race of the individual? What was the cause of death? What kind of death was it? Did the individual have any anatomical peculiarities, signs of disease, or old injuries? Can the individual s height, body weight and physique be estimated? Some basics about bones The normal adult human skeleton has a total of 206 bones. Bones are living, functioning entities and the skeleton is considered to be an organ system. The skeleton functions to support and protect the body. It also provides for the attachment sites for muscles, tendons, and ligaments that allow the body to move. The skeleton also stores minerals (calcium and phosphate) and houses sites that produce red blood cells. Bone tissue can also clean the body by removing heavy metals and other foreign elements from the blood. Marrow is located inside many of the larger bones and is the site of blood cell production. An average of 2.6 million RBC s are produced each second by the marrow to replace those that are worn out and destroyed by the liver. The marrow is also an important part of the production of cells in the immune system. Bone is a complex material with several layers. Compact bone is the outermost layer that is hard and smooth. In long bones, there is an internal layer called the trabecullar bone, which is light and spongy; adding strength to the long bones without increasing the weight. Bone marrow is contained with in the long bones in the medullary cavity. Just like any forensic case, most often you are not left with an entire skeleton to examine, many times not even a whole bone. It may be necessary then to observe the bone using its microstructure. Osteons are special growth cells of bone and are deposited in layers eventually forming chambers. The chambers have canals through which blood vessels travel to reach the cell in the bone. The network of canals is called the Haversian system. Burned bones can even be examined for the presence of Haversian canals. The Haversian canals are especially important for determining if the bone is human or non-human. Bones are classified as long, short, flat or irregular: Long: are longer than they are wide; include bones of the arms, legs, hands and feet Short: approximately as long as they are wide; found in the wrist and the ankle Flat: flat and enclose soft organs; include most bones in the skull, the scapula, sternum, hip bone and ribs ~Forensic Anthropology 2

3 Irregular: irregularly shaped; include the vertebrae and some of the bones in the skull Human bones vs. animal bones Osteology is the study of bones. Human bones and animal bones are different and an expert in anatomy or osteology can identify the differences. Experts can microscopically examine the smaller bones that may be harder to identify, and look at the internal cellular structures. Specifically, osteons, the small holes that carry blood to the bones, are examined looking for an even pattern in humans. Plexiform is a type of bone found not in humans but in other animals. In plexiform bone, the Haversian canals form geometric patterns and are packed tightly with little to no bone between them. Remember, in human bone, the Haverisan canals are evenly spaced and there is bone between them. Estimating Heights The height (stature) of a human can be estimated using one or more of the long bones of the skeleton. The femur, tibia, fibula, humerus, radius, and ulna can be used to calculate height. Some examples are in the charts below. It is important to remember that males and females have different proportions of long bones to total height, so separate equations have been formed. Also, if race has been determined, a separate set of calculations can be used. In this class, we will use calculations specific only to sex, and not include race. If a complete long bone is found, the estimate height can be determined with in a range of +/- 7.5 cm. Estimated height of a female (centimeters): H = femur length X H = tibia length X H = humerus length X H = radius length X FYI: 2.5 cm = 1 inch Estimated height of a male (centimeters): H = femur length X H = tibia length X H = humerus length X H = radius length X Practice: 1. One of the male skeletons found in Gorman had a humerus 34.9cm long. Approximately how tall would that person have been? 2. The body found in a sewer system was found to have a tibia of 34.cm in length. What would the approximate height of the body be if it were a female? How about a male? ~Forensic Anthropology 3

4 3. How tall are you? Once you have determined this, calculate the length range of your humerus bone (the long bone of your forearm). Use the table to see how accurate you are. Gender determination When identifying bones, the gender of the unidentified human is critical. The most obvious location on the pelvis where gender differences can be seen is the sciatic notch. The notch is quite broad with an angle of about 60 o. In males, the angle is much smaller. The shape of the skull, shape of the mandible and the size of the occipital protuberance (bump) at the back of the skull can also determine male or female traits. Males do tend to have larger bones than females, along with larger areas for muscle attachment. The sacrum is straighter in females and more curved in males. The space in the middle of the pelvic bone is larger in women than to make birthing easier. An anthropologist can make a most accurate sex determination by comparing three characteristics of the os pubis: the width of the pubic arch, the width of the pubic body, and the existence of a well-defined ventral arc, a bony ridge on the lower side of the female pubic bone (not usually recognizable until a woman is in her 20s a precursor bone appears about the age of 14). The pubic arch has a larger angle in the female than in the male. The pubic body is narrower in males than in females. Males don t usually have a ventral arc. In older women, the ventral arc will show heavy ridges. Four percent of the female population will not show any ventral arc. In absent cases, the investigator must determine the sex through other characteristics. Age at death A forensic anthropologist can estimate an individual s age at the time of death by examining the biological changes that took place during that person s life. The investigator observes the growth patterns of the teeth, how the bones grew, and epiphyses, or growth plates, and how they formed and united. The closure of the cranial sutures in the skull is also an age indicator. Once a person reaches 25 or 30, the age determination is more difficult and depends on the degenerative changes in the skeleton. The stages of change in the skeleton have been analyzed, however are different in each individual. A range of age is always given to the lead investigator, opposed to an exact age. By looking at the epiphyses, the anthropologist can determine better the age of the individual. General age determinations using epiphyseal union of the medial clavicle Stage of Union Male Female Nonunion without separate 21 or younger 20 or younger epiphysis (no growth plate yet) Nonunion with separate epiphysis (growth plate is formed, but not attached) Partial union Complete union 21 or older 20 or older ~Forensic Anthropology 4

5 General age determinations using epiphyseal union of the iliac crest Stage of Union Male Female Nonunion with out separate 16 or younger 11 or younger epiphysis Nonunion with separate epiphysis Partial union Complete union 17 or older 18 or older Clavicle: also known as the collarbone; its medial ends meet in the center of the body Iliac crest: found on the top of the hipbone Observing the os pubis to determine age Once a person reaches adulthood, bones have stopped growing and changes in the bones are more subtle. The pubic bones and ribs are examined to investigate age of an adult. The pubic symphysis (the space where the left and right hip bones join) has a small amount of cartilage. When the bones are separated and the cartilage is removed, the shape and surface texture can be examined. The symphyseal face of the pubic bone undergoes a regular change from puberty onward. The pattern of the symphysis goes from being in regular rows or furrows in younger people, to a smooth oval surface, and finally to a breakdown of bone in older individuals. In general, the older a person gets, the smoother the surface becomes. Estimating age bases on cranial sutures Sutures are immovable joints where bones are joined together. They are visible as seams on the surface follow the growth of the skull. The sagittal suture is located along the top of the skull, dividing it from right and left, ending at the middle of the back of the skull. The coronal suture goes from the temporal area on one side overtop the skull to the other side. The lambodial suture is found at the very back of the skull. Below are some reference characteristics based on the fusing of the sutures in the skull. If the sagittal suture is completely closed (not visible at any point) o Male = Age 26 or older o Female = Age 29 or older If the sagittal suture is completely open (visible at all points) o Male = Younger than 32 years o Female = Younger than 29 years Therefore, the sagittal suture is not likely to be open if a male is older than 32 and not closed if younger than 26. For a female, the suture is not likely to be open after 29 and not closed if younger than 35. If the skull shows complete closure of all three sutures (no visible suture lines) o Male = Older than 35 o Female = Older than 50 ~Forensic Anthropology 5

6 Images: Answers.com Race determination Forensic anthropology recognizes three major racial groups based on observable skeletal features: Caucasoid (includes European, Middle Eastern, and East Indian descent), Negroid (African, Aborigine, and Melanesian), and Mongoloids (Asian, Native American, and Polynesian). Over time there has been a greater amount of interracial mixing making the distinctions between features for race more difficult to characterize. Race distinctions are determined by examining the skull macroscopically and also mathematically. Caucasoids: have long narrow nasal aperture, triangular palate, oval orbitz, narrow zygomatic arches, and narrow mandibles. Negroids: have a wide nasal aperture, a rectangular palate, square orbits, and more pronounced zygomatic arches. The long bones are also longer and have less curvature and greater density. Mongoloids: have a more rounded nasal aperture, a parabolic palate, rounded orbits, wide zygomatic arches, and more pointed mandibles. Caucasoid Skull Negroid Skull Mongoloid Skull So, now we have a skull but what did they look like? There are two reliable methods for confirming identification based on skull remains. One is photographic superimposition which involves a comparison skull with a photograph of the suspected owner. A video can be taken of the three dimensional image and then a face can be superimposed. The other method is simply to reconstruct the face by compiling tissues using set calculations for the different races and males and females. A proper reconstruction then must require knowing the race and the sex of the individual before beginning reconstruction. Using a measurement table, an anthropologist can use pegs and clay to build up the face by using some guesswork for the lips, nose, eyebrows and so on. This method is not extremely reliable, however have been proven forensically valuable with missing persons. ~Forensic Anthropology 6