Forensic Biology PDF

LESSON 4 | FORENSIC BIOLOGY Individual evidence - belongs to individual person where it Forensic Chemistry belongs you...

LESSON 4 | FORENSIC BIOLOGY Individual evidence - belongs to individual person where it Forensic Chemistry belongs you Example: Fingerprint (DNA) - class evidence ➔ Detection, recognition, and examination of illicit → RELIABLE EVIDENCE IN THE COURT drugs, explosive, and gunshot residue. ➔ Deals with all the tests to detect the presence of various chemicals. COMPOSITION OF BLOOD Forensic Physics 1. RED BLOOD CELLS (Erythrocytes) [44%] ➔ Most abundant cells in our blood ➔ Study of buildings, ballistics, bombs, blood spatters, ➔Produced in the bone marrow and soil, glass and fiber. contain hemoglobin, a protein that carries oxygen to our cells. Forensic Document Examination ➔ NO NUCLEUS = NO DNA Hemoglobin, iron - makes blood red ➔ Examination of disputed documents carry out through scientific methods. ➔ Questioned documents examination is set of 2. WHITE BLOOD CELLS (Leukocytes) [less than standard procedure for comparison and 1%] identification of original and forge documents, ➔ Part of the immune system and destroy disputed will and official papers pathogens ➔ Induced chemicals (xenobiotics) FORENSIC BIOLOGY ➔ Fights diseases, CONTAINS DNA ➔ Section examines evidence for the presence of 3. PLASMA [55%] body fluids such as blood, semen, saliva, DNA ➔ Yellowish liquid portion of blood that analysis, etc. contains electrolytes, nutrients and Body fluids - evidence biological vitamins, hormones, clotting factors, Biology - deals with living organisms and their vital and proteins such as antibodies to fight processes Type of Evidence: infection Chemical evidence - drugs, fire debris ➔ Liquid portion of blood Biological evidence - blood ➔ Contains water (92%) Material evidence - a.k.a. physical evidence Pattern evidence - fingerprints 4. PLATELETS (Thrombocytes) [1%] ➔ Clotting factors that are carried in the Blood plasma ➔ They clot together in coagulation to seal ➔ Class evidence ➔ valuable evidence in many criminal activities a wound and prevent a loss of blood involving physical violence such as murder, ➔ Helps blood to clot assaults, rape, etc. ➔ connective tissue consisting of plasma and formed elements in the cardiovascular system. ➔ transporting oxygen and nutrients to the lungs and tissues. forming blood clots to prevent excess blood loss. BLOOD Blood typing / grouping BPA (Blood Pattern Analysis) Cause of death BLOOD → common evidence ; assault, death investigation Forensic - not first responder ○ They preserve life Follow Criminal Investigation Procedures RCI Evidence Recognizing, identifying, and collecting. LESSON 4 | FORENSIC BIOLOGY statement given by a human may or may not be Blood Typing accurate. In an investigation identified and discovered facts ➔ This type of blood evidence is considered as class are more accurate and reliable than any evidence eyewitness. ◆ Because many people in the world share PRINCIPLE OF ANALYSIS the same blood type This principle states that, “The quality of any ➔ Narrow down suspect analysis would be better by collection of the ➔ Percentage correct sample and its correct preservation in the ◆ Type O - 46% prescribed manner”. ◆ Type A - 40% This leads to better results and avoids ◆ Type B - 10 % tampering, contamination and destruction of a ◆ Type AB - 4% sample. PRINCIPLE OF PROBABILITY HOW TO DETERMINE BLOOD TYPE This law states that, “All identifications (definite or indefinite), made consciously or unconsciously Materials used: on the basis of probability.” Lancet pen - to prick blood from ring finger The perpetrator blood group is also the blood group of various people is high, but the Use anti-sera chemical probability of the same occurring in the case is ○ A - blue color low. ○ B - yellow color ○ D - gray color - determine if + or - CONCLUSIVE EVIDENCE Microscopic slide Evidence which by law cannot be disputed. Toothpick Procedure: CONFIRM THE STAIN IS BLOOD Prick your finger using lancet pen Drop it in 3 microscopic slide 1. KASTLE-MEYER color test Put the anti-sera chemical onto each slide ➔ Mix phenolphthalein and peroxide ; Use a toothpick to mix the blood and the anti-sera reacts with blood to cause a deep chemical. pink color Wait for the clamping/agglutination to happen. ➔ Positive tests for all blood, Agglutination - clumping of particles. NO REACTION OF CLAMPING = NEGATIVE cauliflower and broccoli 2. LEUKOMALACHITE test Result: ➔ Reacts with blood to cause a green color ➔ Positive test for all blood 3. LUMINOL test ➔ Reacts with blood to produce light ➔ Positive tests for all blood, starch, horseradish, and bleach, Blood Samples ➔ Analyzed to determine blood type and DNA, which can be matched to possible suspects disregard control PRINCIPLE OF CIRCUMSTANTIAL FACTS According to this law, “Facts cannot be wrong, they cannot lie not wholly absent but men can and do.” This law emphasizes the significance of circumstantial facts and supports that a LESSON 4 | FORENSIC BIOLOGY Blood Droplets FACTORS AFFECTING SHAPE OF BLOOD DROPLET ➔ Analyzed to give clues to the location of a crime, movement of a victim, and type of SIZE of the droplet weapon ANGLE of the impact VELOCITY at which blood droplet lefts its Blood Spatter origin height ➔ Analyzed to determine patterns that give ❖ Bloodstains can occur on any surface such investigators clues to how a crime might have as carpet, wood, tile, wallpaper, clothing, etc. happened. INTERPRETING BLOOD SPATTER Blood spatter can tell us the following: TEXTURE OF SURFACES Direction blood droplet was moving On a clean glass or plastic, droplet will Where the blood droplet came from have smooth outside edges Type of weapon used in the crime On a rough surface, droplet will produce Position of victim, suspects, and objects scalloping on the edges. Sequence of events. TYPES OF BLOODSTAIN PATTERNS KEYWORDS ★ Passive Bloodstains - created from the force of gravity (drops, pools, flow patterns) ➔ Bloodstains created from the ★ Projected Bloodstains - occur when force is application of force to the SPATTER area where the blood applied to the source of the blood (low/medium/high impact, cast-off, arterial spurting) originated ★ Transfer or Contact Bloodstains - created when a ➔ The place from where the wet bloody object comes in contact with a target ORIGIN / SOURCE blood spatter came from or part. originated ANGLE OF ➔ The angle at which a blood droplet strikes a surface. IMPACT ➔ The droplet from which a PARENT DROP satellite spatter originates ➔ small drops of blood that SATELLITE break of from the parent SPATTERS spatter when the blood droplet hits a surface ➔ The pointed edges of a stain that radiate out from the spatter SPINES ➔ Can help determine the direction from which the blood traveled LESSON 4 | FORENSIC BIOLOGY PASSIVE BLOODSTAINS PROJECTED BLOODSTAINS ➔ Patterns created from the force of ➔ Patterns that occur when a force is applied to the gravity source of the blood ➔ Drop, series of drops, flow ➔ Includes low, medium, or high impact spatters, patterns, blood pools, etc. cast-off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound. DROP SIZE CLASSIFYING SPATTER BY VELOCITY Spatter can be classified by the velocity of the projecting force (not velocity of the blood itself). Size is related to the distance fallen ➔ When a source of blood is Higher = BIGGER drops subjected to a force with a Little change in diameter beyond 1.2m and NO velocity of up to 5 feet per CHANGE after 7ft because the drop reaches second. maximum velocity ➔ Primary stains are usually 4 mm in diameter or greater. LOW VELOCITY BLOOD SPATTER AS EVIDENCE IMPACT SPATTER EXAMPLE: Directionality can be determined by analyzing the (LVIS) tail of the bloodstain. Remember: The tail tells the tale! This spatter often occurs after an The absence of a tail indicates that injury the blood dropped from a 90° angle. This is called a passive ➔ When a source of blood is drop or a gravitational drop. subjected to a force with a velocity of up to 5 to 25 feet per second. ➔ Most stains will range from MEDIUM 1-3mm in size. VELOCITY EXAMPLE: IMPACT SPATTER (MVIS) Beating with fists or blunt objects ➔ When a source of blood is subjected to a force with a HIGH VELOCITY velocity of 30 feet per second or more. IMPACT SPATTER ➔ Most stains will be smaller (HVIS) than 1 mm in size. EXAMPLE: LESSON 4 | FORENSIC BIOLOGY TRANSFER OR CONTACT BLOODSTAINS ➔ These patterns are created when a wet, bloody Gunshot wound object comes in contact with a target surface; may be used to identify an object or body part. ➔ A wipe pattern is created from an object moving through a bloodstain ➔ While a swipe pattern is created from an object leaving a bloodstain. CLASSIFYING SPATTER BY MECHANISM ➔ Bloodstain created when an CLASSIFYING SPATTER BY VELOCITY object moves through an How does the velocity of the impact object affect existing stain. blood spatter? ○ The HIGHER the velocity of impact, the EXAMPLE: SMALLER the size of the spatter. WIPE PATTERN Are these the same patterns you would expect if the blood was traveling at these speeds? Why or why not? ○ No, the patterns are opposite. When the The murder pulls the body across blood itself travels at higher velocity, the the blood stained floor. spatter is larger. ➔ The transfer of blood from a moving source onto an unstained surface. CLASSIFYING SPATTER BY MECHANISM EXAMPLE: SWIPE PATTERN The murder touches the unstained wall with bloody hands as he walks away. Feathered edge shows direction of travel. ➔ Areas that are absent of blood stains in an area that is otherwise full of ➔ Blood that comes out an BACK SPATTER / bloodstains. entrance wound BLOW BACK ➔ Often lands on the weapon EXAMPLES: and/or perpetrator. ➔ Blood associated with an exit VOID PATTERN FORWARD wound. SPATTER Can occur if a bloody item was removed from the scene. LESSON 4 | FORENSIC BIOLOGY Solution: ANGLE OF IMPACT CALCULATION 9𝑚𝑚 18𝑚𝑚 = 0.5 mm −1 Using calculator, convert to 𝑠𝑖𝑛 −1 𝑠𝑖𝑛 (0. 5) = 30° To determine the height: 𝑡𝑎𝑛(30°)𝑥150 = 86 𝑜𝑟 87. String method ➔ Reconstructing bloodstain evidence at crime scenes is a procedure in which individual pieces of string are used to calculate the blood droplet's flight paths, impact angles, and area of origin. 𝑤𝑖𝑑𝑡ℎ 1. To determine the Angle of Impact (AOI) = 𝑙𝑒𝑛𝑔𝑡ℎ Tail is not kasama kapag kukunin ang width at length. However, tail tells the direction. −1 2. Convert the answer to AOI to arcsin or 𝑠𝑖𝑛. 3. Measuring height: Angle of Impact to Area of Convergence = tan(ARCSIN OF AOI) x AOC EXAMPLE: Given: Width = 9mm Length = 18mm Area of Convergence = 150 cm