Forensic Chemistry and Toxicology

Forensic Chemistry and Toxicology Overview

• Forensic chemistry involves the application of chemistry to criminal investigations to analyze evidence.
• A forensic chemist may be called upon to determine if a location served as a clandestine laboratory.
• Examination of marked bills or suspects during extortion entrapment operations may call upon forensic chemistry.

Role of Forensic Chemist in Investigations

• Forensic chemists play a vital role in criminal investigations.
• Their work involves chemical analysis of criminal evidence.
• The role extends to legal proceedings beyond just chemical questions.
• Forensic science areas like legal medicine, ballistics, document examination, dactyloscopy, and photography are all part of forensic chemistry.

Stages and Rules in Forensic Chemistry Work

• Four stages: collecting evidence, examining the specimen, communicating test results, court appearance.
• Six rules: Proceed slowly, be thorough, take detailed notes, consult with others, use your imagination and avoid complicated theories.

Understanding Evidence

• Physical evidence refers to materials related to an investigation that help identify the perpetrator.
• Evidence is proof of an allegation that is sanctioned by law and used to ascertain facts in judicial proceedings.

Classifications of Evidence

• Direct evidence establishes the main fact, based on what witnesses perceive through their senses.
• Circumstantial evidence seeks to establish conclusions via inferences from proven facts.
• Hearsay evidence relies on repetitions of what a witness heard from others rather than personal knowledge.
• Hearsay evidence is generally inadmissible in court with some exceptions.
• Scientific evidence relies on scientific knowledge and techniques.

Types of Scientific Evidence

• Real or autoptic evidence appeals to the senses including hearing, taste, smell, and touch.
• Testimonial evidence is a declaration of truth from an expert witness.
• Experimental evidence involves experiments performed to prove a fact.
• Documentary evidence is written evidence presented in court by an expert.

Witnesses and Suspects

• A witness is a person who provides information about an incident of person.
• Witnesses testify and may include victims, complainants, accusers, or observers.
• A suspect is someone whose guilt is considered a reasonable possibility.

Blood and Bloodstains

• Blood is the body's circulating tissue, composed of cells, enzymes, proteins, and inorganic substances.
• Blood is 45% solid portion (red blood cells, white blood cells, platelets) and 55% liquid portion (plasma).
• Plasma is the yellowish fluid in which blood corpuscles are suspended.
• Serum is the straw-yellow liquid formed when clotted blood stands and contracts. -The study of blood includes where to find it as well as how to correctly collect, preserve, pack, and transport it.
• Blood decomposes quickly.
• Adding Sodium Fluoride to blood may preserve it for one week.

Collection of Blood

• Fluid blood is collected from violent crime victims or those in disputed parentage cases.
• Dried blood is collected from smooth surfaces like walls and floors, or hard surfaces such as tools.
• It's also collected from glaze surfaces, bulky objects, clothing or soil.

Blood Testing

• Preliminary tests determine if a stain is blood: Benzidine, Phenolphthalein, Guaiacum, Leucomalachite Green, Luminol.
• Confirmatory tests confirm the presence of blood Microscopic, Microchemical, Spectroscopic.
• A precipitin test determines if blood is of human or animal origin.

Blood Groupings

• The ABO system, discovered by Lansteiner, includes four groups: O, A, B, and AB.
• Blood types were discovered in the 20th century by Karl Landsteiner who observed that RBCs have antigens.
• The ABO system in humans has four major blood groups: A, B, AB, and O.
• Blood type A has antigen A.
• Blood type B has antigen B.
• Blood type AB has both antigens.
• Blood type O has no antigens.
• Each is either Rh positive or negative, totaling eight major blood groups.
• Knowledge of systems is essential for medical reasons.

Inheritance of Blood Groups and Genetic Factors

• Inheritance is predetermined by the presence/absence of Genes A/B.
• Genes are units in chromosomes that transmit hereditary characteristics and occur in pairs.
• There are two genes or factors: gene A and gene B.
• Phenotypes denote expressed inherited characteristics in the blood group.
• Genotype refers to paired genes.

Rh blood group system

• The Rh blood group system was discovered by Landsteiner and Weiner in 1940.
• The Rh factor was researched with rhesus monkeys on human blood.
• Blood can be Rh positive (+) or negative (-).
• This creates eight blood types.
• The Rh+ genotype masks the Rh- gene.

Presumptive Tests for Blood

• Phenolphthalein uses a solution to show blood presence, based on hemoglobin's peroxidase reaction, producing a pink color.
• Because Phenolphthalein has produced false positives from some substances, it remains presumptive.
• Luminol, applied in solution or sprayed, shows blood via blue fluorescence under UV light.
• Luminol reacts with hematin, producing luminescence best seen in the dark, and can be re-sprayed.
• However, Luminol will show false positives in the presence of of copper salts.

Alternative Light Sources

• Alternative light sources like CrimeScope use UV, visible, or IR light to cause substances to fluoresce (glow) or absorb light (darken).
• Blood stains darken rather than glow when using certain light wavelengths.

Confirmatory Tests for Blood

• Takayama test develops hemochromogen crystals after treating a blood amount or stain with a Takayama-developed solution.
• Takayama test does not require heating and can be used on older samples.
• The RSID test for human blood uses specialized antibodies specific to human Glycophorin A
• NCSCL uses a handheld electronic reader to read confirmatory tests.
• The machine records data on the type and date of test, rendering a result. It also stores a test card image, but they are not stored after down loading.
• Analysis should be evaluated no more than 10 minutes after applying the sample. Kits should be stored at room temperature.

ABA card HemaTrace test strips

• HemaTrace detects blood by identifying human hemoglobin.
• Test strips contain antihuman hemoglobin antibody.
• A complex forms if human hemoglobin is present, migrating to the test window.

Blood Evidence Collection

• The sample must be refrigerated or frozen and delivered to the lab. sample should be thoroughly dried at room temperature.
• Samples must be delivered to laboratory quickly.
• If sample must be mailed, completely air dry it before packing in paper then place into brown paper bag or cardboard box.
• Place one item per container to avoid contamination. Samples should not be put in plastic containers.
• Dried stains can be found on small or large objects, and clothing.
• Large dried objects should be covered with paper and taped to reduce contamination. This method may involve cutting a stained area.

Semen and Seminal Stains

• Semen is a viscid whitish fluid from the male reproductive tract that contains spermatozoa.
• Semen, also called seminal fluid, contains sperm and seminal plasma to keep the sperm cells viable.
• The prostate gland contributes approximately 30% of the seminal fluid.
• The bulbourethral and urethral glands secrete a lubricating protein commonly known as mucus.
• Semen has 200 to 300 million sperm.
• Semen often has a chlorine-like smell and tastes slightly sweet from fructose often.
• About 525 billion sperm are produced in a lifetime.
• 40 million to 1.2 billion sperm cells can be released in a single ejaculation.

Components and Conditions Related to Semen

• Seminal fluid is a component of semen
• Formed cell elements include Spermatozoa or sperm cell.
• Other semen components include epithelial cells, crystals of choline, and lecithin.
• Semen passes through the ejaculatory ducts and mixes with fluids from seminal vesicles for proper composition.
• The seminal vesicles produce a fructose-rich fluid. This forms 65-70% of the semen content.
• Prostrate glands secrete substances which form around 25-30% of the semen content.
• Bulbourethral glands produce a clear secretion, and contribute less than 1% of the overall content.

Semen Conditions and Components

• Aspermia is a lack of spermatozoa in seminal fluid.
• Oligospermia means abnormally low sperm counts.
• Semen may be found fresh in vaginal or rectal contents of a victim.
• Semen may be found as a dry stain on clothing.

Examinations for Seminal Stains

• Physical examinations can be performed.
• There are also chemical examinations which includes : Florence, Barberios Test, Acid-Phosphatase
• Microscopic examination is used to determine spermatozoa presence.
• Visible results appear small object which pear-shaped head behind short neck, tail ten times head length.
• Elements Obstructing Spermatozoa Detection are fabric nature, age of stain, conditions laboratory exposed, handling.
• Biological Examination is available for persons who are secretors.
• Spermato-precipitin is valuable in identifying seminal fluid in bestiality.

Semen Tests

• Acid Phosphatase Test, also known as Walker Test or Brentamine spot test, aids in semen detection.
• The male prostate produces the enzyme acid phosphatase (AP).
• Alpha-Naphthyl acid phosphate and Brentamine Fast Blue produce a dark purple color given AP.
• Alternative light sources are used in the field of chemistry.
• Colors vary due to specialized lights during semen analysis.
• PSA occurs in male prostate gland.
• Caution is used without an actual sperm.

Semen Identification and Sampling

• Christmas Tree Stain is a positive visual in cases.
• Picroindigocarmine stains different areas with green and blue.
• Tails and heads may break down first.
• Rapid Identification is a semen identification series
• Tests can identify semen that has been under favorable locations.
• Items can be stored in the handheld version, for a limited amount of time for safety.

Related Staining

• Gynaecological and obstetrical stains can help with certain cases.
• Hair also has similar identifiers that help locate a body type.
• Stains are considered to be part of medical history
• Sperm can be classified by gametes.

Sperm Cell Collection

• Semen can be collected to view bodily.
• Semen collection is with universal protections.
• Photographic can assist investigation during the case.
• Package the item for easy storage.
• Immovable can be collected.
• If clothing and sample.

Gun Powder

• Most important gun-crime is whether or not they shot a gun.
• Gun-power is needed to assess whether some one has shot something.
• Gun determination or when fired.

Kinds of Gun Powder

• Black powder, charcoal, sulfur and potassium, nitrate.
• Smokeless contains cellulose to reduce stabilizer reactions.

Nitrates during Explosions

• Remnants can be from barrel gun, wounds and clothing.
• Factors or how it affects amount of gasses depending on velocity direction.

Determination of who fired a gun

• Residue in hands can infer the individual shot a weapon.
• DPA test can help determine chemical aspect on the scene.

Possibilities of someone firing a gun

• Person positive for nitrates does not infer when they actually had weapon.
• Powder may become implant on hand.
• Clothing exams can help the powder.

Identification

• Certain tests can help figure out the powder on scene that may have been used.
• To inspect is method is applied and can help understand the time gun has been fired.

Explosives Classified

• Classification of explosives and sudden decomposition of combustion.
• point of view of chemical composition
• low explosives combustive materials.

High Explosives

• High Explosives - materials explode under the influence of shock of the explosion of primary explosive. (e.g. ammonium nitrate, TNT, Dynamite, nitroglycerine, picric acid, and plastic explosive)

Hair and Textiles

• Hair is important examination tool.
• Most crimes occur from some sort of contact either hair, and textiles can help provide insight.

Characteristics of Hair

• Hair is specialized with certain skin types.
• Pointed and strained narrow can infer certain things
• Hair is either considered real or fuzz.

Parts of Hair

• Root is embedded in skin
• Shaft is from the skin.

Medical Index

• The indexes help indicate different diameter.
• Can separate hair through multiple comparisons.

Region and Hair

• Hair is either determined for certain skin-types.
• Is certain regions there is short, hair with stub.
• Children hair is more rudimentary.

Fiber Analysis

• Fiber, that can convert to
• Yarn, twist.

Chemical test

• Tests such as chemical staining, test help determine the overall makeup during tests.
• Can also stain the fiber to infer with the overall identification results.

Glass and Document

• Fiber comes from paper/glass with markings that determine the case.
• Most materials and testing is due to paper and writing.
• Necessary tools are key to knowing document of origin.

Test of paper

• examination is required before
• test can be to much
• can result in an overall review of test.

Glass Composition

• The composition relies of the composition and elements.
• most important, is the components as they may negate data.

Conclusion

• With these types of data all types of cases can be open and shut.
• In any case, it is important to always remember to cross reference data and information to come to a safe conclusion!