Time of Death, Decomposition, and Forensic Entomology

1. Time of Death, Decomposition, and Forensic Entomology Forensic Science K. Davis

2. I. Measuring Body Temperature - Algor Mortis • Normal Body Temperature = 98.6 ˚F (37 ˚C) • After death, the body loses heat at rate of 1.5˚F/hr until it reaches ambient temperature (T of environment). • Rate will vary based on the environment. • Body temperature should be taken rectally or from the liver to be most accurate.

3. Factors that affect algor mortis rate: 1. obesity 2. clothing 3. warm still air 4. exposure to direct sunlight 5. enclosed environment

4. II. Rigor Mortis • Refers to the stiffening and contraction of muscles caused by chemical reactions that take place in the muscle cells after death • Begins throughout body at same time, but muscles become rigid at different rates in a predictable pattern

5. Predictable Pattern of Rigor Mortis 1)  2 hours after death – stiffness detectable in the small muscles of face and neck & then it progresses down toward the toes 2) Next  8 – 12 hours– entire body stiffens 3) Next  18 hours – body remains fixed • (rigid stage of rigor mortis) 4) After the rigid stage – process reverses itself; rigidity is lost in the order that it appeared, starting with small muscles of face • After another 12 hours – muscles are relaxed again • (flaccid stage of rigor mortis) • Rigor mortis is only useful for estimating time of death during first 36-48 hours after death.

6. Things that can alter the rate of rigor mortis: • 1. victim who ran from assailant before death • 2. victims of strychnine poisoning • 3. victim of any fever producing process or heat stroke • In general, heat speeds up the process and cold slows it down. • Not always reliable to determine time of death because the rate can be altered.

7. III. Livor mortis • Refers to dark, purplish discoloration of portions of body • Also called lividity or postmortem hypostasis • Caused by stagnation of blood in vessels and gravity

8. Usually will see lividity most wherever lowest point of body was or where body was pressed against a firm surface • Color of lividity provides clues to ME • ex. Red or pinkish discoloration reveals high levels of oxygen in blood which may be caused by carbon monoxide or cyanide poisoning or exposure to cold temperatures after death • ex. Deep purple lividity may indicate death from severe heart failure, shock or asphyxia and low levels of oxygen in blood

9. Appears  30 minutes – 2 hrs after death • Reaches its maximum 8-12 hrs after death • Can change if body is moved in the first few hours, but becomes fixed after 6-8 hrs • Fixing process is gradual

10. IV. Rate of decay • Decomposition of the body involves two distinct processes: • Autolysis • process of self-ingestion • Enzymes within the body’s cells begin a chemical breakdown of cells and tissues. • Process is hastened by heat and slowed by cold. 2) Putrefaction • Caused by bacteria that destroy body’s tissues • Process is hastened by heat and slowed by cold

11. Decomposition of a pig

12. Occurs in a predictable sequence: • After first 36 hours, the abdomen takes on greenish discoloration that spreads to neck, shoulders, and head. • Bloating begins in the face; caused by gases produced by bacteria • Skin develops blisters or accumulations of fluid • Skin begins to marble • Abdomen swells. • Skin and hair begin to slip from body, and fingernails start to come off. • Body turns greenish-black color and fluids of decomposition drain from body • As the body continues to swell, tissues break open releasing gases and fluids.

13. Internal organs decay in predictable manner: • Intestines decay first, followed by liver, lungs, brain then kidneys • Stomach decomposition is slower because of acids in stomach • Last, uterus or prostate

14. V. Mummification • Occurs when body desiccates (dries out) in a hot, dry environment • Low humidity inhibits bacterial growth, and thus putrefaction, while at same time sucking the moisture from tissues • Process similar to making beef-jerky • In ancient Egypt, spices and salts were rubbed on corpses to hasten the decay

15. VI. Adipocere Formation • Occurs in very wet environments within the body’s adipose (fatty) tissues • Fat literally turns to soap • Result is a white, greasy, waxy substance • It gives the body an unreal, mannequin-like appearance • Most often occurs in bodies found in warm, damp areas • Takes at least 3-6 months to form

16. VII. Floaters • Bodies that die in water or are dumped into water shortly after death initially sink. • Eventually, they rise to the surface because of gases that accumulate in body’s tissues and cavities as putrefaction occurs. • The temperature of the water plays a role. • Display: • Swollen hands and face after 2-3 days • Separation of skin from the body after 5-6 days • Loss of fingernails after 8-10 days • Floating after 8-10 days in warm water and 2-3 weeks in cold water

17. Floater

18. VIII. Eyes • After death, the corneas, or clear covering over the pupils, become cloudy and opaque. • Process may take only a few hours if the eyes were open at death or up to 24 hours if the eyes were closed. • Concentration of potassium within the vitreous humor (thick, jellylike substance that fills your eyeballs) increases slowly during the first few days. • This process is independent of ambient temperature. • Only really accurate though during first few days after death

19. IX. Stomach Contents • After a meal, the stomach usually empties itself in approximately 4-6 hours, depending on type of food ingested. • The small intestine can also be observed for remaining food. • If small intestine is empty, death probably occurred at least 24 hours after victim’s last meal. • If large intestine (colon) is also empty, no food had been ingested for 48-72 hours before death. • This is extremely variable however, depending on individual and type of food.

20. X. ForensicEntomologists • Theyapply their knowledge of entomology to provide information for criminal investigations. • A forensic entomologist’s job may include: • Identification of insects at various stages of their life cycle, such as eggs, larva, and adults. • Collection and preservation of insects as evidence. • Determining an estimate for the postmortem interval or PMI (the time between death and the discovery of the body) using factors such as insect evidence, weather conditions, location and condition of the body, etc. • Testifying in court to explain insect-related evidence found at a crime scene. Did you know? Maggots can be used to test a corpse for the presence of poisons or drugs. Some drugs can speed up or slow down the insect’s development. Cool Jobs: Forensic Entomology Discovery Video

21. Insects as Evidence Forensic entomologists use their knowledge of insects and their life cycles and behaviors to give them clues about a crime. Most insects used in investigations are in two major orders: 1 – Flies (Diptera) and 2 – Beetles (Coleoptera) Blow Fly Carrion Beetle Species succession may also provide clues for investigators. Some species may to feed on a fresh corpse, while another species may prefer to feed on one that has been dead for two weeks. Investigators will also find other insect species that prey on the insects feeding on the corpse. Images: Top Right - http://www.insectinvestigations.com/aboutfe.htm, Chart - http://www.clt.uwa.edu.au/__data/page/112507/fse07_forensic_entomology.pdf

22. Weather data is also an important tool in analyzing insect evidence from a corpse. Investigators will make note of the temperature of the air, ground surface, the interface area between the body and the ground, and the soil under the body as well as the temperature inside any maggot masses. They will also collect weather data related to daily temperature (highs/lows) and precipitation for a period of time before the body was discovered to the time the insect evidence was collected. Other factors that might affect their PMI estimates: Was the body enclosed in an area or wrapped in a material that would have prevented flies from finding the corpse and laying eggs? Were other insect species present that may have affected the development of the collected species? Were there drugs or other poisons in or on the body that might have affected the larvae’s development? http://video.nationalgeographic.com/video/science/health-human-body-sci/human-body/body-farm-sci/ Did you know… The “Body Farm” in Knoxville, Tennessee is a university research facility to investigate human decomposition under various conditions in order to understand the factors which affect its rate. Click the image to view a video about the Body Farm!

23. Blow Fly Metamorphosis Blow flies are attracted to dead bodies and often arrive within minutes of the death of an animal. They have a complete life cycle that consists of egg, larva, pupa, and adult stages. Adult Adult 1st- Adult flies lay eggs on the carcass (ex. at wound areas or around the openings in the body such as the nose, eyes, ears, anus, etc. 2nd- Eggs hatch into larva (maggots) in 12-24hrs. 3rd- Larvae continue to grow and molt (shed their exoskeletons) as they pass through the various instar stages. 1st Instar- 5 mm long after 1.8 days 2nd Instar- 10 mm long after 2.5 days 3rd Instar– 14-16 mm long after 4-5 days 4th- The larvae (17 mm) develop into pupa after burrowing in surrounding soil. 5th- Adult flies emerge from pupa cases after 6-12days. Pupa Pupa Eggs Eggs 1stInstar Larva 1stInstar Larva 3rdInstar Larva 3rdInstar Larva 2ndInstar Larva 2ndInstar Larva It takes approximately 14-16 days from egg to adult depending on the temperatures and humidity levels at the location of the body. Image: http://www.umext.maine.edu/images/FlyLife.jpg Information: http://www.kathyreichs.com/entomology.htm and http://www.forensicentomologist.org/

25. Certain circumstances can change schedule • Blowflies for example, don’t deposit eggs at night and are less plentiful during winter. • Insect studies most often provide a minimum time that has elapsed since death.

26. Examples of Diptera (Flies) Early Stage Decomposition Blow & Greenbottle Flies (Calliphoridae) Metallic thorax and abdomen Flesh Fly (Sarcophagidae) Striped thorax Life Cycle of a Calliphoridae Fly Late Stage Decomposition House Fly (Muscidae) Cheese Skipper (Piophilidae) Informational Source: http://naturalsciences.org/files/documents/csi_tg_overview.docImages: Top Left - http://www.scienceinschool.org/repository/images/issue2forensic3_large.jpg, Middle-Left: http://forensicfact.files.wordpress.com/2008/04/blowfly053.jpg, Top Right - http://users.usachoice.net/~swb/forensics/P1.jpg, Bottom - http://www.deathonline.net/decomposition/corpse_fauna/flies/index.htm

27. Examples of Coleoptera (Beetles) Early Stage Decomposition Early to Late Stage Decomposition Carrion Beetles (Silphidae)Adults & larvae feed on fly larvae Rove Beetles (Staphylinidae) Predator of fly eggs Clown Beetles (Histeridae) Predator of fly eggs Late Stage Decomposition Ham & Checkered Beetles (Cleridae)Predator of flies & beetles; also feed on dead tissue Hide Beetles (Scarabidae)Usually the last to arrive Skin Beetles (Dermestidae)Feed on dried skin & tissues Informational Source: http://naturalsciences.org/files/documents/csi_tg_overview.doc Images: http://www.cals.ncsu.edu/course/ent425/library/spotid/coleoptera/coleoptera.html & http://www.forensicflies.com/beetles.htm

28. Let’s give it a try … Click the image above or click here to visit the website at http://www.pbs.org/wnet/nature/episodes/crime-scene-creatures/interactive-determine-the-time-of-death/4390/

29. XI. Scene Markers • ME will use all information available to determine time of death, including many non-scientific findings. • Examples • Broken watch or clock • Victim who missed work for 2 days and is found near his or her front door, dressed in work attire, and holding car keys, probably was heading to work at time of death.