Hidden in them BONES...

Forensic identification of skeletal remains

     One of the first things established is whether or not the bones are human. If there are intact long bones or a skull, this finding can be fairly straight forward. If the bones are fragmented, however, it becomes more difficult to judge. Human bones vary significantly in both size and shape. Bear paws are often mistaken for human feet. Pet rabbits and guinea pigs are also mistaken for human fetal remains.

How long have the bones been buried?

     If the osteologist determines the remains are human, the next question to answer is antiquity of the burial. Generally in forensic investigations, 50-75 years antiquity is the cut-off time, according to Forensic Pathology: Principles and Practices by David Dolinak, Evan Matshes and Emma Lew. Forensic investigations focus on solving a crime. If the burial occurred more than 50-75 years ago, it is unlikely a criminal prosecution will occur. But the missing individual's relatives will still want to know if the remains belong to their loved one.

     Antiquity can be difficult to establish. It often depends on the retrieval of non-biological artifacts such as clothing, buttons, dental implants or work, and medical implants or procedures. Each of these items can usually be assigned a manufacture date or a time period in which they were used. Museum curators and other staff can help identify the ages of various objects.

How many bones should we look for?

     Another common question is: "How many bones are we looking for?" There is no correct answer because unless officials know the victim's age, they will not know the number of bones they seek. The British Broadcasting Corp.'s (BBC's) Science and Nature Web site reports that a fetus has somewhere between 275 and 300 bones, a baby or infant has 275 or less depending on age, and an adult human has 206 bones.

How old was the person?

     Age can be determined by looking at the growth plate, also known as the epiphysis or epiphyseal plate, found at the end of many bones. As a person ages these plates ossify and fuse to adjoining bone, a process that occurs at a fairly predictable rate. Most bones fuse by the time a person reaches 25, after which time the bones begin losing density and show wear patterns.

     In adults, the pelvis and skull can help estimate age. The shape of the ends of the ribs and the pubic symphysis also may aid these estimates. In youth, the pubic symphysis appears rippled. As a person ages it becomes increasingly smooth; by age 50 the ripples have generally disappeared. The degree of rippling is rated using the Todd Method's 1-10 scoring system.

     The skull also can indicate age because the sutures that join its bones fuse at a known rate according to age. Keep in mind that there is always a margin of error — maturation differs from individual to individual. In addition, sex, genetic predisposition, nutrition and disease also can affect this rate.

     Some sources suggest measuring a skeleton's long bones can also help calculate age. But while long bone measures are fairly accurate in the skeletons of fetuses and young children, after age 4 or 5 this accuracy diminishes.

     Examining dentition is the most accurate method of age determination because teeth erupt at a fairly standard rate. At birth the margin of error is +/- two months. By the age of 15, the margin of error increases to +/- three years. Again variable maturity rates between the sexes can create significant error. It is advisable when examining children's remains to determine the person's sex first.

What sex was the victim?

     Determining sex in adult skeletal remains is said to be one of the easier tasks asked of the osteologist. When the hip bones, skull or an entire skeleton are present, some researchers place the accuracy at 95 percent. When only the skull is found, accuracy drops a bit but still stands at 80-92 percent. Even without the skull and hip bones, it is possible to determine sex given the differences in female and male knee joints, report Dolinak, Matshes and Lew. In general, males have more robust bones and more prominent muscle attachments.

     However, despite these differences in stature, the female sacrum (tailbone area) is wider and oval in shape for childbirth. In women who have had children, there is a pitting or rippling on the pubis surface. Known as dorsal pitting, the rippling tells the examiner the remains are from a female of childbearing age. However, this feature does not indicate the number of children the woman has had, and Dolinak, Matshes and Lew speculate that some dorsal pitting may be caused by increases in weight not childbirth.

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