Human Remains

The Postmortem Interval: Determining the Time of Death

A pathologist can do this most accurately within the first 24 hours using algor, livor, and rigor mortis.

After 24 hours, estimations are made using environmental factors or other forensic evidence from the scene.

Algor mortis refers to the cooling rate of the body after death. Generally, the body cools by about 1 to 1 ½ degrees per hour from 98.6 degrees at death until it reaches the environmental temp.

The Glaister formula can be used to determine the number of hours elapsed since death:

h=(98.4 - internal temp.)/1.5

(Used up to 36 hours after death, most accurate within 12.)

Livor mortis refers to the pooling of blood in the body after the heart stops, due to gravity.

There is none where the body touches the ground or is otherwise constricted.

Begins within ½ hour of death and is most evident at 12 hours, after which the discoloration will not change regardless of how the body is disturbed.

Used to determine whether a body has been moved.

Rigor mortis refers to the rigidity of skeletal muscles after death.

It first appears in the face, neck, and jaw (small muscles), then in the larger muscles of the trunk, arms, and legs.

Occurs within 2 to 3 hours and disappears in approx. 30 hours.

Forensic Anthropology The use of knowledge of the skeletal

system to identify crime victims and determine cause and circumstance of death.

Is it human or animal? The study of bones is called osteology. Humans and animals have different skeletal

structures, different bones and differently shaped bones.

Microscopically, bones contain holes, or osteons, that carry blood. Animal osteons form a regular pattern, while those in humans do not.

The Skeleton An adult human has 206 bones! The skeleton provides structure and protection. Muscles are connected to bone by tendons;

bones are connected to each other and joints by ligaments.

Bones are classified into four groups:long—arms, legs, hands, feetshort—wrist, ankleflat—skull, scapula, sternum, hip, ribsirregular—vertebrae, skull

Estimating Height using long bones

Female (in cm, +/-7.5)

H= femur length x 2.21 + 61.41

H= tibia length x 2.53 + 72.57

H= humerus length x 3.14 + 64.97

H= radius length x 3.87 + 73.50

Male (in cm, +/-7.5)

H= femur x 2.23 + 69.08

H= tibia x 2.39 + 81.68

H= humerus x 2.97 + 73.57

H= radius x 3.65 + 80.40

Determining Sex Using the Os Pubis—the pelvic bones have

the most obvious differences between men and women

The pubic arch has a larger angle in females

The pubic body is narrower in malesThe ventral arc is usually absent in

males

Male vs. female pelvis

Using the skull—there are several differences between men and women in the sizes and shapes of the bones in the skull

Male Female

Fore-head

Sloping Vertical

Zygo-matic arch

Wide Narrow

Man-dible

Large Narrow

Male Female

Chin Square Pointed

Ascending ramus

Wide Narrow

Mastoid process Large Small

Male Female

Nuchal crest Large, rugged Small, smooth

Determining Age An investigator can reasonably estimate a

person’s age at death by studying the biological changes that took place during that person’s life.

The investigator can estimate most accurately when teeth are erupting, bones are growing, and epiphysis (growth plates) are forming and uniting.

The diaphysis, makes up most of the length of the long bone. Epiphyses are found at both ends; their function is to allow for growth.

The epiphyses are good places to look for changes in estimating age. Though all people grow at different rates, there are similarities that make generalizations possible.

After the normal growth period, about 25 to 30 years, age estimation becomes more difficult and depends on degenerative changes in the skeleton.

The bones of the skull come together along serrated, interlocking joints called sutures. These sutures allow for growth of the skull.

Closure of cranial sutures in the skull are also an age indicator. The 3 major sutures are the sagittal, coronal, and lamboidal.

If the sagittal suture is completely closed: Male >26, Female >29

If the sagittal suture is completely open: Male <32, Female <35

If the skull shows complete closure of all 3 major sutures: Male >35, Female >50

Another way to determine age is to examine the pubic symphysis, the area where the two hip joins come together in front.

As a person ages, the bones rub together, producing wear patterns that range from regular rows to smooth to breakdown of bone.

Determination of Race There are three major anthropological racial

groups based on observable skeletal features: Caucasoid—European, Middle Eastern, East

Indian Negroid—African, Aborigine, Melanesian Mongoloid—Asian, Native American, Polynesian

Skeletal Characteristics Caucasoid

Long, narrow nasal aperture Triangular palate Oval orbits Narrow zygomatic arches Narrow mandible

Negroid Wide nasal aperture Rectangular palate Pronounced zygomatic arches Longer bones with less curvature and greater

density

Mongoloid Rounded nasal aperture Parabolic palate Rounded orbits Wide zygomatic arches Pointed mandibles

Facial Reconstruction When remains cannot be identified by

traditional means, a forensic artist may try facial reconstruction.

Steps include: Establish gender, age, and race Glue tissue markers to landmarks Mark muscle insertion points Select data set for exact thickness

Mount eyes Apply clay Measure for nose and mouth Cover with layers of skin, add details

Proportion is more important than accuracy in recognition.

Cause of Death and Bone Anomalies

Sometimes the cause of death is obvious—stab wounds, bullet holes, and blows to the head all leave marks on a skeleton.

Investigators need to be sure that the marks were the result of the crime and not earlier injury or scavenger marks from animals.

Healed breaks or fractures, joint replacements, and evidence of bone disease can help in identification.

Forensic anthropology uses osteology, archaeology, pathology, photography, art and crime scene investigation in identifying unknown remains--both modern and ancient—of victims of crime, disaster, or unknown causes.