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Body fluids chap 6
| Question | Answer |
|---|---|
| Secretion | refers to the production of substances that are useful for the organism, like saliva, mucus, or hormones. |
| Excretion | involves the elimination of waste from the body, such as sweat, urine, and feces. |
| Hematology | studies blood |
| serology | focuses on blood plasma and body fluids in general, including their role in crime investigations, such as toxicology and cause of death. |
| plasma | (55% of blood) consists of 90% water and 10% dissolved substances like proteins and lipids. |
| Blood cells | include B-cells that produce antibodies, essential in identifying blood types and triggering immune responses. |
| ABO blood system | categorizes blood based on antigens (A and B) on red blood cells (RBCs). The combination of these antigens, inherited from both parents, determines a person’s blood type (e.g., A, B, AB, or O). |
| Agglutination | (clumping) of RBCs indicates the presence of specific antibodies in the serum and helps determine blood type. For instance, mixing anti-B antibody with blood type B results in agglutination. |
| Rh factor | (D-antigen) determines whether blood is Rh+ or Rh-. Blood types are typically described as A+, A-, B+, B-, AB+, AB-, O+, and O-. |
| blood transfusions | matching both ABO and Rh factors is crucial to avoid immune reactions. However, there are other Rh antigens, such as C, c, E, and e, but these are not usually considered in blood transfusions. |
| Blood typing helps | narrow down suspects by matching blood types, but it cannot conclusively establish identity. Additional evidence is needed for conviction. |
| frequency of blood types | varies by population, so blood type alone is not sufficient to determine origin or ancestry. |
| Environmental factors, such as | temperature, humidity, and chemical contamination, can degrade blood antigens, making typing difficult or inconclusive. |
| Mixed blood samples | (from multiple individuals) can complicate analysis, especially if there are multiple victims or the assailant’s blood is present. |
| Recent blood transfusions | might also interfere with blood typing results, requiring careful consideration by investigators. |
| paternity tests | blood typing is used primarily for inclusion or exclusion. The blood types of the mother and presumptive father can be used to support or dispute paternity claims. |
| What differentiates secretion from excretion? | Secretion produces substances that are useful to the organism (e.g., saliva), whereas excretion involves eliminating waste (e.g., sweat, urine). |
| What is the role of blood typing in criminal investigations? | Blood typing is used to narrow down suspects by matching blood types but cannot establish a specific identity. It is useful for inclusion/exclusion, but the presence of blood from multiple individuals or environmental degradation can make it inconclusive |
| How do blood transfusions impact forensic blood typing? | Recent blood transfusions can interfere with blood typing results, requiring extra caution during analysis. |
| What are the limitations of blood typing for determining country of origin or ancestry? | Blood type distributions vary by population, but the frequency of a particular blood type is too widespread for it to accurately pinpoint country of origin or ancestry. |
| Limitations of Using Blood Typing for Identification: | Blood typing cannot establish the identity of an individual. Specific antigens degrade quickly in certain environments. Large samples of blood are often needed for accurate results. Recent blood transfusions can affect the accuracy of blood typin |
| Key Questions in Crime Scene Blood Analysis: | Where is the blood? Is this blood? Is the blood human? How are the blood stains distributed? |
| Cleaning efforts | may leave small, hard-to-find blood stains behind, especially in hard-to-reach places like cracks in floors or under heavy furniture. |
| Latent blood | can be hard to detect in cleaned areas, but small amounts often remain even in meticulously cleaned locations. |
| Everyday activities | (like shaving or cutting meat) can result in blood that has no connection to a crime, making it crucial to differentiate between crime-related and non-crime-related blood. |
| Presumptive Blood Tests: | Presumptive tests detect the presence of blood, but they don’t confirm it. They rely on the reaction of heme (in hemoglobin) with various substances that result in luminescence, fluorescence, or color changes. |
| Fluorescein (Fluorescence Test): | Fluorescein is a highly sensitive method that can detect blood at very low concentrations (1:105,000 dilution). It works by reacting with heme from red blood cells and producing a green fluorescence under UV light. Pros: Effective for detecting traces o |
| Luminol (Chemiluminescence Test): | Luminol reacts with heme to produce a blue glow (425nm wavelength), which can be observed even under infrared illumination. Sensitivity: It can detect blood at concentrations of 1:100,000 (and even up to 1:1,000,000 under infrared light). Pros: Can dete |
| Alternative Light Sources (ALS) for Blood Detection: | ALS uses light in the UV (350-395nm) or infrared (850-1500nm) range. |
| Blood under ALS | Blood is not fluorescent itself but appears as a darkened area. Plasma and serum are more visible, showing better contrast. |
| Coagulated blood | Appears with a darker center surrounded by a glowing halo of serum. |
| IR ALS: | Detects blood stains as darker areas, especially useful on complex fabrics with various patterns and colors. |
| Kastle-Meyer Test: | This test is less effective when used with certain food products like potatoes, horseradish, and other fruits and vegetables, which can cause false positive results. |
| Animal blood: | Can be difficult to differentiate from human blood, especially when dealing with old stains or when multiple species’ blood is mixed, particularly in outdoor crime scenes with many animals. |
| Radial Diffusion Method: | This method uses species-specific antibodies in agarose gel to distinguish human from animal blood. As the sample diffuses, a ring forms, indicating the presence of human blood. |
| Rapid Stain Identification Series (RSID): | Developed by the FBI for rapid identification of human body fluids at the crime scene. A suspected stain is scraped, dissolved in a buffer solution, and applied to a sample well. If human blood is present, the test line will darken. Two lines (test and co |
| Polymerase Chain Reaction (PCR): | Amplifies specific DNA segments (e.g., mitochondrial DNA, mtDNA) from blood samples, enabling the determination of whether the blood is human. |
| DNA Barcoding | Can differentiate between multiple species in a mixed blood sample. This is especially useful when a sample contains blood from more than one individual or species. |
| Alternative Light Sources (ALS) | help with non-contact detection of blood and are effective for detecting blood on various surfaces, including complex fabrics. |
| Kastle-Meyer test | can give false positives with certain food items. |
| Differentiating between human and animal blood | is essential in criminal investigations, especially in environments with multiple species or in outdoor crime scenes. |
| RSID | is an efficient tool for rapid detection of human blood on the scene, reducing unnecessary sample collection. |
| PCR | is a critical tool for DNA analysis, allowing the identification of human blood and distinguishing between multiple species in mixed samples. |
| Bloodstains and Crime Scene Analysis | Blood patterns help determine what happened during a crime, such as the type of injury, weapon used, victim and assailant positions, and movement during/after the crime. Blood behaves according to physics but can change based on internal (e.g., diseases, |
| Passive Stains: | Caused by gravity; includes drops, flows, and pools. |
| Drops: | Blood drips from a stationary source, such as a weapon or finger |
| Flows: | Blood flows due to gravity; helps determine body position or movement after injury. |
| Pools: | Accumulated blood on a surface over time, which can show time since death. |
| Transfer Stains: | Created when blood is transferred from one surface to another (e.g., bloody handprint). |
| Impact Stains | Result from forceful actions (e.g., spatter from a beating). |
| Factors Affecting Bloodstains | Height: The higher the drop, the larger the diameter (until terminal velocity is reached). Angle: A 90° angle results in a round drop; as the angle decreases, the drop elongates. Surface Texture: Smooth surfaces create round drops, while rough surfaces |
| Flow: | Blood moves due to gravity, indicating body position and movement after injury. |
| Changes in Flow Direction | Can indicate body movement after blood started to flow. |
| Blood Pooling | Blood pools form on surfaces after prolonged bleeding, and the appearance changes over time (affected by clothing, temperature, humidity). Pools can help estimate time since death and indicate movement or interference with the pool. |
| What affects the shape and size of a bloodstain? | Drop height, impact angle, and surface texture. |
| What information can bloodstain analysis provide? | Details about the weapon used, injury type, victim/assailant positions, and movement during/after the crime. |
| Wipe Pattern: | Created when an object moves over existing blood, changing its appearance (e.g., wiping with a cloth). |
| Swipe Pattern: | Formed when a bloody object moves and contacts an unstained surface (may leave a print). |
| Pattern Transfer: | Occurs when a bloody object leaves a recognizable print (e.g., bloody handprint or shoeprint). |
| Impact Stains | Caused by a forceful action, typically when an object hits liquid blood. Blood spreads in two directions: back spatter (towards the attacker) and forward spatter (away from the attacker). |
| Low Velocity: | Blunt force trauma (speed 1.5-8 m/s; droplets 1-4 mm). |
| High Velocity: | Gunshot wounds (speed >30 m/s; mist-like spatters, droplets <1 mm). |
| Cast-Off Patterns | Produced by repetitive blows (e.g., stabbing, blunt force trauma). Helps determine the type of weapon, number of blows, and attacker/victim positions |
| Arterial Spurts: | Blood from an artery, caused by heart pumping, with a wave-like, pulsating pattern. |
| Expiration Spatter: | Blood expelled by air pressure from the lungs (e.g., coughing or sneezing). Coughing (80 km/h) creates fine mist-like droplets. Sneezing (300 km/h) expels smaller particles with air bubbles. |
| Clotted Stains | Occur as blood clots after bleeding. Clotting patterns help identify movement (e.g., dragging the body). |
| Diluted Stains | Result from the addition of liquids (e.g., attempts to clean blood). |
| Diffused Stains | Blood may spread due to physical interaction (e.g., moving objects or bodies). |
| Dried Stains | Occur when blood dries over time. |
| Insect-Altered Stains | Blood patterns disturbed by insects |
| Voids | Areas where blood is missing, indicating something blocked the blood path. |
| Photography | Photograph bloodstains with rulers for size and proportion. |
| Positioning & Movement | Shape and distribution help determine victim/attacker positions and movements. |
| Angles & Calculations | Angles of impact can be determined using trigonometry to understand spatter direction and position. |
| Transfer Pattern | Object alters existing bloodstain. |
| Impact Stain | Forceful action (back and forward spatter). |
| Projection Pattern: | Blood expelled from the body due to pressure (e.g., arterial spurt, expiration spatter). |
| Altered Stains | Changes due to clotting, dilution, or other interference. |
| Angle of Impact & Blood Droplet Size: | These factors help determine the position of the body at the time of injury and bleeding onset. Analyzing multiple blood drops, especially their angles, helps identify the point of convergence—the area where the blood originated. The 3D location of the |
| Stringing Method | Involves using elastic strings to visualize and measure angles of blood stains, which helps determine the direction of blood travel and the position of the origin. Modern techniques use computer software for faster, more accurate processing. |
| Challenges in Estimations | The estimates become less precise when the victim moves (e.g., from multiple gunshots or injuries). Multiple spatter profiles can make it difficult to determine the exact sequence of events |
| saliva | is primarily water (99.5%) and contains enzymes (like amylase and lipase), electrolytes, immunoglobulins, and antibacterial compounds. It lubricates the mouth and aids in digestion and taste. |
| Forensic Significance in saliva | Saliva is often associated with sexual assaults, fights (where blood and saliva mix), or the use of items like masks. It can also help determine the position of a body, especially in cases of hanging or strangulation. |
| Alternative Light Sources (ALS) | are used to detect saliva, especially dried saliva, which fluoresces under UV light. |
| Phadebas Test: | Uses a dye linked to starch that reacts to salivary amylase. |
| Phadebas Test limitations: | Cannot distinguish human from animal saliva. The intensity of the blue color is not quantifiable. It may not detect amylase in soil, where degradation of proteins is high. |
| Semen (Seminal Fluid) | Produced by: Male reproductive organs (testes, prostate, seminal vesicles). Components: Sperm cells (spermatozoa), enzymes, fluids. Volume: 3ml per ejaculation. pH: 7.2–8 (alkaline). Color: Translucent white to yellow. |
| semen Challenges with forensic evidence | Low sperm count (oligospermia), absence of sperm (azoospermia) due to vasectomy, or sperm cell degradation in condoms over time. |
| semen under ALS (Alternative Light Source) | Fluoresces semen stains, especially under UV/blue light. |
| Acid Phosphatase Test | Presumptive, turns purple if semen is present. |
| Microscopic Examination: | Sperm cells visible (KPIC stain) for confirmation. |
| In Situ Hybridization: | Distinguishes male vs. female cells using X/Y chromosomes. |
| Vaginal Fluid and Discharge | Produced by: Vaginal wall, cervix, uterus. Components: Epithelial cells, white blood cells, bacteria. pH: 3.8-4.2 (protects against pathogens). Content: Glycogen, acids, lipids, proteins. Purpose: Protects and lubricates vagina, inhibits sperm movemen |
| Vaginal Fluid and Discharge Detection at Crime Scene | Challenges: Hard to detect when mixed with semen or blood. ALS: Fluoresces under long-wavelength light (green-blue). |
| PAS and Lugol’s Test: | Detect glycogen, but can react with other cells. |
| Vaginal Peptidase Test: | Specific for vaginal fluid (no false positives). |
| Lactic to Citric Acid Ratio: | Helps distinguish vaginal fluid from semen. |
| Semen Detection | Sperm cells required for DNA, tested with microscopy or phosphatase tests. |
| Vaginal Fluid Detection: | Focus on glycogen, peptidase, and lactic acid content. |
| Which is NOT a contributor to vaginal discharge? | The ovary (it's the cervix, vagina, and uterus that contribute). |
| Urine | Production: Formed by the kidneys through blood filtration, then transported via ureters to the bladder and expelled through the urethra. Appearance: Pale yellow; color depends on hydration (clear if hydrated, amber if dehydrated). Can indicate health is |
| Urine at Crime Scenes: | Found in cases of sexual assault, harassment, or involuntary release due to fear or death. Can indicate toxins, drugs, hormones, and medical conditions. DNA isolation from urine is difficult due to low epithelial and white blood cells (better in females |
| DMAC Test: | Turns pink when urine is present (can give false positives). |
| Jaffe Test: | Detects creatinine (not always accurate). |
| RSID™ Urine: | Most reliable; detects Tamm-Horsfall glycoprotein, confirming human urine. |
| Urine detection challenges | Urine is highly diluted and spreads easily, making stains faint. Low DNA content, especially in male urine. |
| Feces | Formation: Excreted by the digestive system, consisting of undigested food, water, and waste products. Appearance: Brown due to bile and bilirubin. Color changes can indicate diet or health issues (e.g., red = blood, green = undigested bile). |
| Feces at Crime Scenes: | Rare but may appear in cases of property desecration, assault, or involuntary release (fear, death). Can contain useful evidence like diet, parasites, and DNA. Can link a person to a crime scene (e.g., through plant material, seeds, or parasites). |
| feces Detection: | Smell and Appearance: Most obvious indicator. Microscopy: For plant material, seeds, fibers, and parasites. Urobilinogen Test: Detects urobilinogen, but can also be found in urine. Molecular Tests: Real-time PCR detects bacteria-specific genes like Bac |
| feces challenges | Low epithelial cells and high bacteria can affect DNA quality in feces. Requires specialized tests to confirm and link feces to a specific individual. |
| Urine is challenging for | DNA due to low cell content, especially in males. It is most useful for confirming toxins or drug presence. |
| Feces can contain | DNA, diet info, and evidence of parasites but is challenging to extract reliable DNA due to bacterial content. |
Created by:
JuliaLoft