Serology, Forensic Pathology, & Entomology

1. Serology, Forensic Pathology, & Entomology

2. Serology • Serology- study of blood and other bodily liquids • Semen • Sweat • Saliva • Gastric Juices

3. Blood • Functions of Blood • Transport of nutrients, wastes, and hormones • Defense against pathogens • Stabilization of body temperature • Composition of blood • Plasma: liquid portion of blood (46-63%) • Cellular Components • Red cells (erythrocytes) • White cells (leukocytes) • Platelets (thrombocytes)

4. Types of Red Blood Cells • Landsteiner: Discovered blood typing through blood transfusions (transfer of blood into another’s blood stream) • Classification system: A, B, AB, O, Rh+, Rh- • Based on antigens on surface of red blood cell

5. Blood & Forensics • Until 1990s, use of blood for ID based on blood typing assuming no 2 people have same blood (except twins) • > 100 factors, or antigens on red blood cells • Factors controlled by individual genetics • Now can use DNA typing as __________ evidence • ABO & Rh currently considered class evidence. Why? • Comparisons made by the product rule (of probability)

6. Blood Probability Question • What is the probability that someone else in the population has this combination of antigens? • A positive, M-, N positive, S positive • Antigen Incidence in General population A 42% B 12% AB 3% O 43% Rh 85% M 30% N 27% S 48%

7. One more Question • Probability of O negative, M positive, N-, S- • Antigen Incidence in General pop’n A 42% B 12% AB 3% O 43% Rh 85% M 30% N 27% S 48%

8. Is It Really Blood? • Questions to be answered when collecting (in order) • Is the sample blood? • Is the sample animal blood? • If animal blood, from what species? • If human blood, what type? • Can the sex, age, and race of the source of blood be determined?

9. Question 1: Is it really blood? Presumptive tests cause color change Tests rely on presence of hemoglobin 1. Kastle Meyer Test (Phenolphthalein) • Water- helps to pick up substance onto swab • Ethyl Alcohol- cleans any debris and exposes heme • Hydrogen peroxide- H2O2 • Heme- removes oxygen from hydrogen peroxide (H2O2) • Results in water + oxygen • Phenolphthalein (KM)- “oxygen hungry”- takes free oxygen & turns pink in color - test =not likely blood + test (pink) = blood False positive: looks like it should be blood when it really is not

10. Question 1: Is it really blood? Cont’d Hemastix Luminol Chemical sprayed on carpet and furniture Slight phosphorescent light in dark where there are blood stains (and certain other stains) are present Emission of light (in dark room) is positive • Dipsticks easy to carry • When used at crime scene, turn green if blood

11. Questions 2 & 3: Is the Sample Human or Animal Blood? • Precipitation Test- to determine if blood human or not • Based on rabbit antibodies to human blood • Blood placed in antiserum tube • Non-human blood reacts with antibodies in antiserum • Form precipitin band

12. Question 4: If human, what is its type? • Test antigen of red blood cell • Stimulates body to make antibodies against it • If antibody matches antigen, RBC will agglutinate ( or clump)

14. Interpreting Agglutination (clumping) • If clumps, that is the blood type • Coagulation (clumping) & hemolysis (cell burst) occurs if antigen comes in contact with antibody

15. Blood Typing Punnett Squares • Blood Type A: AA or AO • Blood Type B: BB or BO • Blood Type AB: AB • Blood Type O: OO AB x BO OO x AB Heterozygous= AO Homozygous = AA, BB, OO

16. Forensic Pathology • Postmortem investigation of sudden or unexpected death or trauma to the living • Conduct autopsies

17. What Happens During An Autopsy? External Internal

18. Role of Forensic Pathologist During an Autopsy 4 broad determinations to be made: • Cause of Death – reason someone dies • Mechanism of Death – specific change in body that ended life • Manner of Death • 1. Homicide 2. Suicide 3. Accidental4. Natural Causes • D. Time of Death Example Cause of death: Shooting Mechanism of Death: Loss of blood Manner of Death: Homicide Time of Death: 13 hours

19. Cause of Death: Traumas • Determine type of wound • Measure the dimensions (length, width, depth) • Position relative to anatomical landmarks • Determine initial location if wound involves cutting, slashing, etc. • Determine height fromheel

20. Traumas: Types of Wounds Stab Wound • Cuts • Lacerations • Incised • Puncture • Abrasion- scrape Abrasion

21. Types of Wounds: Cont’d • Contusion- bruise • Color changes a bruise goes through can give rough estimate of time of injury • Dark blue/purple (1-18 hours) • Blue/brown (~1 to 2days) • Green (~ 2 to 3 days) • Yellow (~3 to 7 days) • Assumes person is healthy.

22. Types of Wounds: Cont’d • Gunshot • Things for pathologist to learn: • type of firearm • distance of gun to victim • entrance vs exit wounds • track of projectile Starring occurs when gun pressed against skin Stippling- gun powder burns when gun inches from skin

23. Time of Death • Can estimate time of death from • Normal postmortem changes • Algor mortis • Livor mortis • Rigor mortis • Decomposition • Insect action (forensic entomology) • Stomach contents (stage of digestion) • Last known activity (last sighting, newspaper/mail)

24. Normal Postmortem Change 1: Algor mortis • Cooling rate of the body after death • Hour estimate: [98.6 oF – internal temp]/1.5 • Works up to 36 hours • Body loses 1.4°F per hour in first 12 hours • Body loses 0.7°F per hour after first 12 hours • Must also account for environmental temp, type of clothing on body, if wet, air movement, if person is heavyset or lightset

25. Normal Postmortem Change 2: Livor Mortis • Livor Mortis: Pooling of blood in the body after the heart stops, caused by gravity • Looks purple or red • Begins half hour after death • After 12 hours, pooled blood will not move if body disturbed • Helps to identify if the body has previously been moved

26. Normal Postmortem Change 3: Rigor Mortis • Rigor Mortis- Rigidity of skeletal muscles after death • Muscles relax, ATP breaks down, change in fluid concentration in muscle • First seen in small muscles: face, neck, jaw • Lasts up to 30 hours after death

27. Postmortem Changes: Rigor Mortis

28. Stages of Decomposition • A. Fresh Stage (Days 1-2) • Commences at death, ends when bloating is first evident. Breakdown of protein and carbohydrates into simpler compounds • B. Bloated Stage (Day 2-6) • Putrefaction begins. Gasses produced by anaerobic bacteria inflate the abdomen. • C. Decay Stage (Days 5-11) • Abdominal wall breaks allowing gasses to escape. Carcass deflates. • D. Post-decay Stage (Days 10-25) • In dry habitats, remains are skin, cartilage, and bones. In wet habitats, wet, viscous material in the soil under the remains. • E. Dry Stage (Days 25+) • Mainly bones and hair remain. Odor is primarily that of normal soil and litter. Can last several months to years.

29. What Speeds Up & Slows Down Decay Speed Up! Slow Down Cold temps Sleeping before death Obese Less sun exposure Healthy Less clothing • Warm Temps • Aerobic exercise before death • Thin body weight • Greater sun exposure • Illness • More clothing

30. Stomach Analysis

31. Forensic Entomology • Insect involvement in events such as murder, rape • Can determine time since death based on succession of insects in the body

32. Blowfly Life Cycle