Anth345 "Forensic Science" Final Exam Notes
Anth345 "Forensic Science" Final Exam Notes Anth345
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Chapter 12: Forensic Toxicology 11/29/2015 ▯ “Father of Toxicology” Mathieu Orfila ▯ Headline News: What killed Napoleon? Napoleon I was sent into exile after his defeat on the island of St. Helen, that was filled with hot, unsanitary and rampant with disease He was confined to a large reconstructed agricultural building known as Longwood House Boredom and unhealthy living conditions gradually took their toll on Napoleon’s mental and physical state o He suffered from severe abdominal pain and experienced swelling of the ankles and a general weakness of his limbs He died May 5, 1821 from what an autopsy concluded to be stomach cancer It was inevitable that dying under British control, as Napoleon did, would bring with it numerous conspiratorial theories to account for his death o One of the more fascinating inquiries was conducted by a Swedish dentist, Sven Forshufvud, who systematically correlated the clinical symptoms of Napoleon’s last days to those of arsenic poisoning The truth rested in Napoleon’s hair Forshufvud arranged to have Napoleon’s hair measured for arsenic content by neurtron activation analysis and found it consistent with arsenic poisoning over a lengthy period of time ▯ What is the role of Forensic Toxicology? Toxicologists detect and identify drugs and poisons in body fluids, tissues, and organs Their services go beyond legal institutions such as crime laboratories and medical examiners’ offices, they also reach into hospital laboratories, where the possibility of identifying a drug overdoes may represent the difference between life and death and into various health facilities responsible for monitoring the intake of drugs and other toxic substance ▯ Toxicology of Alcohol Knowing how the body metabolizes alcohol provides the key to understand its effects on human behavior This knowledge has also made it possible the development of instruments that measure the presence and concentration of alcohol in individuals suspected of driving while under the influence Metabolism of Alcohol: o All chemicals that enter the body are eventually broken down by chemicals within the body and transformed into other chemicals that are easier to eliminate o This process of transformation, called metabolism, consists of three basic steps: absorption, distribution, and elimination Metabolism: The transformation of a chemical in the body to another chemical to facilitate its elimination from the body Absorption and Distribution: Alcohol or ethyl alcohol is a colorless liquid normally diluted with water and consumed as a beverage During the absorption phase, alcohol slowly enters the body’s bloodstream and is carried to all parts of the body o Absorption: passage of alcohol across the wall of the stomach and small intestine into the bloodstream Once this phase is complete, the alcohol becomes distributed uniformly throughout the watery portions of the bodythat is, throughout about two-thirds of the body volume After absorption is completed, a max alcohol level is reached in the blood, and the post- absorption period begins Many factors determine the rate at which alcohol is absorbed into the bloodstream including: o Time taken to consume the drink o Alcohol content of beverage o Amount consumed o And quantity and type of food present in the stomach at the time of drinking Elimination: As the alcohol is circulated by the bloodstream, the body begins to eliminate it Alcohol is eliminated through two mechanisms: oxidation and excretion o Oxidation: the combination of oxygen with other substances to produce new products o Excretion: Elimination of alcohol from the body in an unchanged state; alcohol is normally excreted in breath and urine Nearly all of the alcohol consumed is eventually oxidized to carbon dioxide and water Takes place almost entirely in the liver o There, in the presence of the enzyme alcohol dehydrogenase, the alcohol is converted into acetaldehyde and then to acetic acid The remaining alcohol is excreted, unchanged, in the breath, urine and perspiration ▯ Inside the Science: Alcohol in the Circulatory System Measuring the quantity of alcohol present in the blood system is accomplished in one of two ways: o By direct chemical analysis of the blood for its alcohol content or… o By measurement of the alcohol content of the breath Humans, like all vertebras, have a closed circulatory system, which consists basically of a heart and numerous arteries, capillaries and veins An artery is a blood vessel carrying blood AWAY from the heart, and a vein is a vessel carrying blood back TOWARD the heart Capillaries are tiny blood vessels that interconnect the arteries with the veins Ingestion and Absorption of alcohol and the circulatory system: o After alcohol is ingested, it moves down the esophagus into the stomach o About 20% of the alcohol is absorbed through the stomach walls into the portal vein of the blood system o The remaining alcohol passes into the blood through the walls of the small intestine o Once in the blood, the alcohol is carried to the liver, where its destruction starts as the blood (carrying the alcohol) moves up to the heart o The blood enters the upper right chamber of the heart, called the right atrium (or auricle) and is forced into the lower right chamber of the heart, known as the right ventricle o Having returned to the heart from its circulation through the tissues, the blood at this time contains very little oxygen and much carbon dioxide o Consequently, the blood must be pumped up to the lungs, through the pulmonary artery, to be replenished with oxygen Aeration: o The respiratory system bridges with the circulatory system in the lungs, so that oxygen can enter the blood and carbon dioxide can leave it o The lungs contain about 250 million alveoli, all located at the ends of the bronchial tubes o The bronchial tubes connect to the windpipe (trachea), which leads up to the mouth and nose o At the surface of the alveolar sacs, blood flowing through the capillaries comes in contact with fresh oxygenated air in the sacs o A rapid exchange now proceeds to take place between the fresh air in the sacs and the spent air in the blood o During breathing, the carbon dioxide and alcohol are expelled through the nose and mouth, and the alveoli sacs are replenished with fresh oxygenated air breathed into the lungs, allowing the process to begin all over again The distribution of alcohol between the blood and alveolar air is similar to the example of a gas dissolved in an enclosed beaker of water Here again, one can use Henry’s Law to explain how the alcohol divides itself between the air and blood Henry’s Law may now be restated as follows: When a volatile chemical (alcohol) is dissolved in a liquid (blood) and is brought to equilibrium with air (alveolar breath), there is a fixed ratio between the concentration of the volatile compound (alcohol) in air (alveolar breath) and its concentration in the liquid (blood) and this ratio is constant for a given temperature The temperature at which the breath leaves the mouth is normally 34 degrees Celsius o At this temp. experimental evidence has shown that the ratio of alcohol in the blood to alcohol in alveoli air is approx. 2,100 to 1 In other words, 1 milliliter of blood will contain nearly the same amount of alcohol as 2,100 milliliters of alveolar breath Recirculation and Distribution: o After emerging from the lungs, the oxygenated blood is rushed back to the upper left chamber of the heart (left atrium) by the pulmonary vein o When the left atrium contracts, it forces the blood through a valve into the left ventricle, which is the lower left chamber of the heart Artery: A blood vessel that caries blood away from the heart Vein: A blood vessel that transports blood toward the heart Capillary: A tiny blood vessel across whose walls exchange of materials between the blood and the tissues takes place; it receives blood from arteries and carries it to veins Alveoli: Small sacs in the lungs through whose walls air and other vapors are exchanged between the breath and the blood The fate of alcohol in the body is therefore relatively simple – namely, absorption into the bloodstream, distribution throughout the body’s water, and finally, elimination by oxidation and execration. The elimination, or “burn off” rate of alcohol varies in different individuals; 0.015 % w/v (weight per volume) per hour is the average rate after the absorption process is complete. However, this figure is an average that varies by as much as 30% among individuals ▯ Testing for Intoxication: Breath Testing for Alcohol: o A device for collecting and measuring the alcohol content of alveolar breath o A breath test measures the alcohol concentration in the pulmonary artery by measuring its concentration in alveolar breath o Tests obtained during the absorption phase may be higher than results obtained from a simultaneous analysis of venous blood Breath-test Instruments: o The first widely used instrument for measuring alcohol content of alveolar breath was the Breathalyzer, developed by R. F. Borkenstein o Unlike the breathalyzer, modern breath testers are free of chemicals These devices include infrared light-absorption devices and fuel cell detectors Fuel cell-detector: A detector in which chemical reactions produce electricity Infrared and fuel-cell-based breath testers are microprocessor controlled, so all an operator has to do is press a start button; the instrument automatically moves through a sequence of steps and produces a readout of the subjects test results Considerations in breath testing: o The key to accuracy of a breath-testing device is to ensure that the unit captures the alcohol in the alveolar (deep-lung) breath of the subject o Subject must blow for a minimum time of 6 seconds o The breath-test instruments just described feature a slope detector, which ensures that the breath sample is alveolar, or deep-lung breath. o A major consideration is to avoid measuring “mouth alcohol” resulting from regurgitation, belching, or recent intake of an alcoholic beverage o Measurement of independent breath samples taken within a few minutes of each other is another extremely important check of the integrity of the breath test ▯ Inside the Science: Infrared Light Absorption Any alcohol present in the subject’s breath flows into the instrument’s breath chamber A beam of infrared light is aimed through the chamber, a filter is used to select a wavelength of infrared light at which alcohol will absorb As the infrared light passes through the chamber, it interacts with the alcohol and cause the light to decrease in intensity The decrease in light intensity is measured by a photoelectric detector that gives a signal proportional to the concentration of alcohol present in the breath sample The information is processed by an electronic microprocessor, and the percent blood-alcohol concentration is displayed on a digital readout Also, the blood alcohol level is printed on a card to produce a permanent record of the test results Most infrared breath testers aim a second infrared beam into the same chamber to check for acetone or other chemical interferences on the breath If detected differences is relative response of two infrared beams that does not conform to ethyl alcohol, the operator is immediately informed of the presence of an “interferant” ▯ Field Sobriety Testing These preliminary, or field sobriety tests are normally performed to ascertain the degree of the suspect’s physical impairment and whether an evidential test is justified Field sobriety tests usually consist of a series of psychophysical tests and a preliminary breath test o A portable handheld roadside breath tester o Horizontal-gaze nystagmus, walk and turn, and the one-leg stand constitute a series of reliable and effective psychophysical tests o Horizontal-gaze nystagmus is an involuntary jerking of the eye as it moves to the side o Walk and turn and the one-leg stand are divided-attention tasks, testing the subject’s ability to comprehend and execute two or more simple instructions at one time Walk and turn requires the suspect to maintain balance while standing heel-to-toe and at the same time listening to and comprehending the test instructions ▯ Analysis of Blood for Alcohol Gas chromatography is the approach most widely used by forensic toxicologists for determining alcohol levels in blood Under proper conditions alcohol can be separated from other volatile substances in the blood By comparing the resultant alcohol peak area to ones obtained from known blood-alcohol standards, the investigator can calculate the alcohol level with a high degree of accuracy Another procedure for alcohol analysis involves the oxidation of alcohol to acetaldehyde o This reaction is carried out in the presence of the enzyme alcohol dehydrogenase and the coenzyme nicotine-amide- adenine dinucleotide (NAD) ▯ Inside the Science: The Fuel Cell A fuel cell converts energy arising from a chemical reaction into electrochemical energy A typical fuel cell consists of two platinum electrodes separated by an acid or base containing porous membrane A platinum wire connects the electrodes and allows a current to flow between them In the alcohol fuel cell, one of the electrodes is positioned to come into contact with a subject’s breath sample If alcohol is present in the breath, a reaction at the electrode’s surface converts the alcohol to acetic acid One by-product of this conversion is free electrons, which flow through the connecting wire to the opposite electrode, where they interact with atmospheric oxygen to form water The fuel cell also requires the migration of hydrogen ions across the acidic porous membrane to complete the circuit The strength of the current flow between the two electrodes is proportional to the concentration of alcohol ▯ Collection and Preservation of Blood Once blood is removed from an individual, it is best preserved sealed in an airtight container after adding an anticoagulant and a preservative The blood should be stored in a refrigerator until delivery Anticoagulant: a substance that prevents coagulation or clotting of blood o EDTA or potassium oxalate prevent clotting Preservative: A substance that stops the growth of microorganisms in blood o Sodium fluoride, inhibits the growth of microorganisms capable of destroying alcohol One study performed to determine the stability of alcohol in blood removed from living individuals found that the most significant factors affecting alcohol’s stability in blood are storage, temperature, the presence of a preservative, and the length of storage Failure to keep the blood refrigerated or to add sodium fluoride resulted in a substantial decline in alcohol concentration Alcohol and the Law Blood-Alcohol Laws: o American Medical Association and the National Safety Council in specifying that a person with a blood-alcohol concentration in excess of 0.15 % w/v was to be considered under the influence of alcohol o Was than lowered to 0.10 % w/v o In 2000, the U.S. federal law established 0.08 % as the per se blood-alcohol level, meaning that any individual meeting or exceeding this blood-alcohol level shall be deemed intoxicated Constitutional Issues: th o The 5 Amendment to the U.S. Constitution guarantees all citizens protection against self-incrimination – that is, against being forced to make an admission that would prove one’s own guilt in a legal matter o To prevent a person’s refusal to take a test for alcohol intoxication on the constitutional grounds of self- incrimination, the National Highway Traffic Safety Administration (NHTSA) recommended an “implied consent” law o In accordance with this statute, operating a motor vehicle on a public highway automatically carries with it the stipulation that the driver must either submit to a test for alcohol intoxication if requested or lose his or her license for some designated period – usually 6 months to a year o Supreme Court case Schmerber v. California Addressed the constitutionality of collecting a blood specimen for alcohol testing, as well as for obtaining other types of physical evidence from a suspect without consent While being treated at LA hospitals for injuries sustained during an automobile collision, Schmerber was arrested for driving under the influence of alcohol A physician took a blood sample from Schmerber at the direction of the police, over the objection of the defendant On appeal to the U.S. Supreme Court, the defendant argued that his privilege against self-incrimination had been violated by the introduction of the results of the blood test at his trial The Court ruled against the defendant, reasoning that the Fifth Amendment only prohibits compelling a suspect to give “testimonial” evidence that may be self- incriminating; being compelled to furnish “physical” evidence, such as fingerprints, photographs, measurements, and blood samples, the Court ruled, was not protected by the Fifth Amendment The Court also addressed the questions of whether Schmerber was subjected to an unreasonable search and seizure by taking of blood specimen without a search warrant The Court upheld the blood removal, reasoning that the natural body elimination of alcohol created an emergency situation allowing for a warrantless search ▯ The Role of the Toxicologist Toxicologist: An individual charged with the responsibility of detecting and identifying the presence of drugs and poisons in body fluids, tissues, and organs Challenges Facing the Toxicologist: o Without supportive information, the toxicologist must use general screening procedures with the hope of narrowing thousands of possibilities to one o A toxicologist is not dealing with drugs at the concentration levels found in powders and pills, by the time a drug specimen reaches the toxicology laboratory, it has been dissipated and distributed throughout the body o The body is an active chemistry laboratory, and no one can appreciate this observation more than a toxicologist o Few substances enter and completely leave the body in the same chemical state o A thorough understanding of how the body alters or metabolizes the chemical structure of a drug is essential in detecting its presence o When and if the toxicologist has surmounted all of these obstacles and has finally detected, identified, and quantitated a drug or poison, he or she must assess the substance’s toxicity ▯ Collection and Preservation of Toxicological Evidence: Toxicology is made infinitely easier once it is recognized that the toxicologist’s capabilities are directly dependent on the input received from the attending physician, medical examiner, and police investigator Generally, with a deceased person, the medical examiner decides what biological specimens must be shipped to the toxicology laboratory for analysis However, with a living person suspected of being under the influence of a drug presents a completely different problem, and few options are available When possible, both blood and urine are taken from any suspected drug user The entire urine void is collected and submitted for toxicological analysis Preferably, two consecutive voids should be collected in separate specimen containers When a licensed physician or registered nurse is available, a sample of blood should be collected ▯ Techniques Used in Toxicology: Acids and Bases o Like the drug analyst, the toxicologist must devise an analytical scheme to detect, isolate, and identify a toxic substance o The first chore is to selectively remove and isolate drugs and other toxic agents from the biological materials submitted as evidence Acids: A compound capable of donating a hydrogen ion (H+) to another compound Acid Drugs: Barbiturates, Acetylsalicylic acid (aspirin) Base: A compound capable of accepting a hydrogen ion (H+) Basic Drugs: Phencyclidine, Methadone, Amphetamines, Cocaine pH scale: A scale used to express the basicity or acidity of a substance; a pH of 7 is neutral, whereas lower values are acidic and higher values are basic Screening and Confirmation: o Once the specimen has been extracted and divided into acidic and basic fractions, the toxicologist can identify the drug present o The strategy for identifying abused drugs entails a two-step approach: screening and confirmation A screening test is normally employed to give the analyst quick insight into the likelihood that a specimen contains a drug substance This test allows a toxicologist to examine a large number of specimens within a short period of time for a wide range of drugs Any positive results from a screening test are tentative at best and must be verified with a confirmation test The three most widely used screening tests are thin-layer chromatography (TLC), gas chromatography (GC), and immunoassay Gas chromatography/mass spectrometry is generally accepted as the confirmation test of choice Detecting Drugs in Hair: o Most drugs remain in the bloodstream for about 24 hours; urine, they normally are present for 72 hours o Drugs present in blood diffuse through the capillary walls into the base of the hair and become permanently entrapped in the hair’s hardening protein structure o As the hair continues to grow the drug’s location on the hair shaft becomes a historical marker for delineating drug intake ▯ Detecting Nondrug Poisons: Heavy Metals: The forensic toxicologist only occasionally encounters a group of poisons known as heavy metals o These include arsenic, bismuth, antimony, mercury, and thallium o To screen for many of these metals, the investigator may dissolve the suspect body fluid or tissue in a hydrochloric acid solution and insert a copper strip into the solution o Such a finding must be confirmed by the sue of analytical techniques suitable for inorganic analysis – namely, atomic absorption spectrophotometry, emission spectroscopy, or X- ray diffraction Carbon Monoxide: Unlike heavy metals, carbon monoxide still represents one of the most common poisons encountered in a forensic laboratory o When carbon monoxide enters the human body, it is primarily absorbed by the red blood cells, where it combines with hemoglobin to form carboxyhemoglobin o An average red blood cell contains about 280 million molecules of hemoglobin o However, if a high percentage of the hemoglobin combines with carbon monoxide, not enough is left to carry sufficient oxygen to the tissues, and death by asphyxiation quickly follows o Two basic methods for measuring the concentration of carbon monoxide in the blood: Spectrophotometric methods examine the visible spectrum of blood to determine the amount of carboxyhemoglobin relative to oxyhemoglobin or total hemoglobin Also, a volume of blood can be treated with a reagent to liberate the carbon monoxide, which is then measured by Gas Chromatography o The amount of carbon monoxide in blood is generally expressed as percent saturation This represents the extent to which the available hemoglobin has been converted to carboxyhemoglobin o In a healthy middle aged individual, a carbon monoxide blood saturation greater than 50-60% is considered fatal ▯ Significance of Toxicological Findings For many drugs, blood concentration levels are readily determined and can be used to estimate the pharmacological effects of the drug on the individual When dealing with a living person, the toxicologist has the added benefit of knowing what a police officer may have observed about an individual’s behavior and motor skills, as well as the outcome of a drug influence evaluation conducted by police officer trained to be a drug recognition expert ▯ Case Files: Joann Curley: Caught by a Hair Joann Curley rushed her husband Bobby to a general hospital in Pennsylvania after Bobby started experiencing an attack that required medical attention Bobby experienced a burning sensation in his feet, numbness in his hands, a flushed face, and intense sweating o He was diagnosed with Guillain-Barre syndrome An acute inflammation of the nervous system After being discharged Bobby experienced another bout of debilitating pain and numbness o He was admitted to Hershey Medical Center in Hershey Pennsylvania There doctors observed extreme alopecia or hair loss Test results of Bobby’s urine showed a high level of the heavy metal thallium in his body o Thallium, a rare and highly toxic metal that was used decades ago in substances such as rat poison and to treat ringworm and grout Bobby’s doctors could now treat him for thallium poisoning but before they could do so, Bobby went into cardiac arrest and slipped into a coma Joann Curley made the decision to remove him from life support, and he died shortly after Investigators learned that Bobby had changed his life insurance to list his wife, Joann, as the beneficiary of his $300,000 policy The toxicologist conducted segmental analysis of Bobby’s hair, an analytical method based on the predictable rate of hair growth on the human scalp (an average of 1 centimeter per month) The hair analysis proved that Bobby Curley was poisoned with thallium long before he began working as an electrician (he started 5 months before his death) at Wilkes University The first few doses were small, which probably barely made him sick at the time Gradually, over a year or more, Bobby was receiving more doses of thallium until he finally succumbed to a massive dose three or four days before his death After careful scrutiny of the timeline, investigators concluded that only Joann Curley had access to Bobby during each other these intervals, and she also had a motive, in the amount of $300,000 Presented with the evidence, Joann Curley pleaded guilty to murder and confessed that she had poisoned Bobby with rat poisoning she had found in her basement ▯ Case Files: Michael Jackson: The Demise of a Superstar Michael Jackson was unconscious, suffering from cardiac arrest when responders arrived at his house When the initial autopsy revealed no foul play, rumors started of a possible drug related death News media showed investigators caring bags full of drugs and syringes out of Jackson’s home, so it was no surprise when the forensic toxicology report accompanying Jacksons autopsy showed that the entertainer had died of a drug overdose Jackson had become accustomed to receiving sedatives to help him sleep Early morning of his death, his physician gave him a tab of Valium At 2 am he administered the sedative lorazepam And at 3 am the physician administered another sedative, midazolam All these drugs were then administered again at 5 am and 7:30 am But Jackson still could not sleep Finally at 10:40 Jackson’s doctor gave him 25 milligrams of propofol, at which point Jackson went to sleep o Propofol is a powerful sedative used as surgical anesthesia All the drugs administered into Jacksons system were sedatives, which can act in concert to depress the activities of the CNS It was no surprise that the drug cocktail resulted in cardiac arrest and death ▯ Case Files: Accidental Overdose: The Tragedy of Anna Nicole Smith Anna was found unconscious in her hotel room, she was taken to Memorial Legal Hospital, where she was declared dead at age 39 Analysis of Smith’s blood postmortem revealed an array of prescribed medications o Most pronounced was a toxic level of the sedative chloral hydrate o Although many of the drugs in Anna’s system were at levels consistent with typical doses of the prescribed medications, it was their presence in combination with chloral hydrate that exacerbated the toxic level of chloral hydrate The lethal combination of these prescription drugs caused failure to both her circulatory and respiratory systems and resulted in her death The investigators determined that the overdose of chloral hydrate and other drugs was accidental and not a suicide ▯ The Drug Recognition Expert The LAPD developed and tested a series of clinical and psychophysical examinations that a trained police officer could use to identify and differentiate between types of drug impairment This program has evolved into a national program to train police as drug recognition experts Normally 3-5 month training program is required to certify an officer as a drug recognition expert (DRE) The DRE program incorporates standardized methods for examining suspects to determine whether they have taken one or more drugs The process is systematic and standard; to ensure that each subject has been tested in an routine fashion, each DRE must complete a standard Drug Influence Evaluation form The entire process takes about 30-40 minutes The DRE evaluation process can suggest the presence of the following seven broad categories of drugs: o Central nervous system depressants o Central nervous system stimulants o Hallucinogens o Dissociative anesthetics o Inhalants o Narcotic analgesics o Cannabis The DRE program is not designed to be a substitute for toxicological testing The toxicologist can often determine that suspect has a particular drug in his or her body The DRE can supply credible evidence that the suspect was impaired at a specific time and that the nature of the impairment was consistent with a particular family of drugs BUT the DRE usually cannot determine which specific drug was ingested ▯ Components of the Drug Recognition Process The Breath-Alcohol Test o Obtaining accurate and immediate measurement of the suspects blood-alcohol concentration Interview with the Arresting Officer o Spending a few minutes with the arresting officer often enables the DRE to determine the most promising areas of investigation The Preliminary Examination o Structured series of questions, specific observations and simple tests provides the first opportunity to examine the suspect closely The Eye Examination o Certain drugs induce nystagmus, and involuntary spasmodic motion of the eye ball Divided-Attention Psychophysical Tests o Tests that check balance and physical orientation and includes the walk and turn, one-leg stand, Romberg balance and the finger to nose Vital Signs Examination o Precise measurements of BP, PR, and body temperature are taken Dark Room Examinations: o The size of the suspect’s pupils in room light, near-total darkness, indirect light, and direct light is checked Examination for Muscle Rigidity o Certain categories of drugs cause the muscles to become hypertensive and quite rigid Examination for Injection Sites o Users of certain categories of drugs routinely or occasionally inject their drugs Suspect’s Statements and Other Observations o Attempt to interview the suspect concerning the drug or drugs he or she has ingested Opinions of the Evaluator o Using the info obtained in the previous ten steps, the DRE can make an informed decision about whether the suspect is impaired by drugs and, if so, what category or combination of categories is the probably case of the impairment The Toxicological Examination o The DRE should obtain a blood or urine sample from the suspect for lab analysis in order to secure scientific, admissible evidence to substantiate his or her conclusions ▯ The Green River Killer In 1982, within six months the bodies of 5 females were discovered in or near the Green River Most of the victims were known prostitutes who were strangled and apparently raped By the end of 1986 the body count in the Seattle region had rose to 40, all of whom were believed to have been murdered by the Green River Killer Investigators focused their search on Gary Ridgway, a local truck painter He passed his initial lie detector test With a search warrant in hand, police searched Ridgway’s residence and also obtained hair and saliva samples from Ridgway Again, insufficient evidence caused Ridgway to be released from custody As the investigation continued, a DNA link between Ridgway and his victims eluded investigators A careful microscopic search of Ridgway’s clothing revealed the presence of paint spheres of various colors, which compared to spheres on the clothing of six of the victims The paint was microscopically and chemically identified as lmron, a high end specialty paint that was manufactured before 1984 This paint was used at the truck plant where Ridgway worked and was identified as dried paint spheres emanating from a spray paint Forensic Analysis of Trace Elements For the criminalist, the presence of trace elements is particularly useful because they provide “invisible” markers that may establish the source of a material or at least provide additional points for comparison Glass fragments represent a valuable type of trace evidence; however, generally because of their minute size they present the criminalist with two direct issues o First, classifying the type of glass being examined Float glass (windows, windshields) Container glass (bottles, jars) Borosilicates (kitchenware) Up to 25 different elements have been identified in glass ▯ Evidence in the Assassination of President Kennedy There has been a heavy debate since President Kennedy’s assassination on whether Lee Harvey Oswald was apart of a conspiracy to assassinate the president or if he was a lone assassin ▯ The Emission Spectrum of Elements We have already observed that molecules can readily be characterized by their selective absorption of ultraviolet, visible, or infrared radiation Equally significant to the analytical chemist is the knowledge that elements also selectively absorb and emit light These observations form the basis of an important analytical technique designed to determine the elemental composition of materials – emission spectroscopy Types of Spectra o Emission spectrum: light emitted from a source and separated into its component colors or frequencies o Continuous spectrum: A type of emission spectrum showing a continuous band of colors all blending into one another o Line spectrum: A type of emission spectrum showing a series of lines separated by black areas; each line represents a definite wavelength or frequency ▯ Atomic Structures Scientists now know that the atom is composed of even more elementary particles that are collectively known as subatomic particles o The most important subatomic particles are: Protons: A positively charged particle that is one of the basic structures in the nucleus of an atom Electrons: A negatively charged particle that is one of the fundamental structural units of the atom Neutrons: A particle with no electrical charge that is one of the basic structures in the nucleus of an atom o The nucleus of the atom is composed of positively charged protons and neutrons, which have no equal to the number of negatively charged electrons in orbit around the nucleus Nucleus: The core of an atom, containing the protons and neutrons o Hydrogen: has a nucleus consisting of one proton and no neutrons, and one orbiting electron o Helium: has a nucleus comprising two protons and two neutrons, with two electrons orbiting around the nucleus Atomic Number: The number of protons in the nucleus of an atom; each element has its own unique atomic number An element is therefore a collection of atoms that al have the same number of protons ▯ Inductively Coupled Plasma Emission Spectrometry (ICP) ICP identifies and measures elements through light energy emitted by excited atoms However, instead of using an electrical arc, the atoms are excited by placing the sample in a hot plasma torch The torch is designed as three concentric quartz tubes through which argon gas flows The ICP Process: o Begins when a high-voltage spark is applied to the argon gas flowing through the torch o This strips SOME electrons from the argon atoms o These electrons are then caught and accelerated in the magnetic field such that they collide with other argon atoms, stripping off still more electrons o The collision of electrons and argon atoms continues, argon ions, and electrons and forming an inductively coupled plasma discharge The discharge is sustained by RF energy that is continuously transferred to it from the coil o The plasma discharge acts like an intense continuous flame, generating extremely high temps in the range of 7,000- 10,000 degrees Celsius ▯ Isotopes and Radioactivity Atomic Mass: The sum of the number of protons and neutrons in the nucleus of an atom Atoms with the same number of protons but differing solely in the number of neutrons are called isotopes o Isotopes: An atom differing from another atom of the same element in the number of neutrons in its nucleus Many isotopes are quite stable, and for all intents and purposes, the isotopes of any one element have indistinguishable properties Others, however, are not as stable and decompose with time by a process known as radioactive decay o Radioactivity is the emission of radiation that accompanies the spontaneous disintegration of unstable nuclei Radioactivity: The particle and/or gamma-ray radiation emitted by the unstable nucleus of some isotopes Composed of three types of radiation: alpha particles, beta particles and gamma rays Alpha particle: A type of radiation emitted by a radioactive element; the radiation is composed of helium atoms minus their orbiting electrons Beta particles: A type of radiation emitted by a radioactive element; the radiation consists of electrons Gamma-ray: A high-energy form of electromagnetic radiation emitted by a radioactive element o Isotopes are dangerous when ingested The radioisotope polonium-210, an emitter of alpha particles, was implicated in the murder of an ex-KGB agent o Nuclear Reactor: A source of neutrons that can be used to bombard the atoms of a specimen, thereby creating radioactive isotopes ▯ Neutron Activation Analysis: The technique of bombarding specimens with neutrons and measuring the resultant gamma-ray radioactivity One major advantage of this is that it provides a nondestructive method for identifying and quantitating trace elements o A median detection sensitivity of one-billionth of a gram (one nanogram) makes neutron activation analysis one of the most sensitive methods available for the quantitative detection of many elements A major drawback to the technique is its expense and regulatory requirements Has been used to characterize trace elements present in metals, drugs, paint, soil, gunpowder residues, and hair o Typical illustration of its application occurred during the investigation of a theft of copper telegraphic wires in Canada Four lengths of copper wire (A1, A2, A3, A4) found at the scene of the theft were compared by neutron activation with a length of copper wire (B) seized at a scrap yard and suspected of being stolen All were bare, single-strand wire with the same general physical appearance and diameter of 0.28 centimeters Prior experiments had revealed that significant variations could be expected in the concentration levels of the trace elements selenium, gold, antimony, and silver for wires originating from different sources ▯ Forensic Examination of Paint Most prevalent of physical evidence received by the crime lab Hit-and-run and burglary cases are most common Criminalist must compare two or more paints to establish their common origin Composition of Paint The binder provides the support medium for the pigments and additives and it a polymeric substance Paint is thus composed of a binder and pigments, as well as other additives, all dissolved or dispersed in a suitable solvent Most common types of paint examined in the crime lab is finishes from automobiles o The automotive finishing system for steel usually consists of at least four organic coatings Electrocoat primer: First layer applied to the steel body of a car is the electrocoat primer Primer consists of epoxy-based resins Provides corrosion Primer Surfacer: Are epoxy-modified polyesters or urethanes The function of this layer is to completely smooth out and hide any seams or imperfections because the color coat will be applied on this surface Highly pigmented Basecoat: This layer provides the color and aesthetics of the finish and represents the “eye appeal” The integrity of this layer depends on its ability to resists weather, UV radiation, and acid rain A growing trend towards pearl luster or mica pigments Mica pigments are coated with layers of metal oxide to generate interference colors Clearcoat: Unpigmented clearcoat is applied to improve gloss, durability, and appearance Most clearcoats are acrylic based but polyurethane clearcoats are increasing in popularity ▯ Microscopic Examination of Paint Microscope is most important instrument Paint color, more than any other property, imparts paint with its most distinctive forensic characteristics The importance of layer structure for evaluating the evidential significant of paint evidence cannot be overemphasized When paint specimens possess colored layers that match in number and sequence of colors, the examiner can begin to relate the paints to a common origin Unfortunately, most paint specimens presented to the criminalist do not have a layer structure of sufficient complexity to allow them to be individualized to a single source ▯ Analytical Techniques Used in Paint Comparison Characterization of Paint Binders o Pyrolysis gas chromatography has proven to be a particularly invaluable technique for distinguishing most paint formulations Paint chips as small as 20 micrograms are decomposed by heat into numerous gaseous products and are sent through a GC o Pyrolysis: Decomposition of organic matter by heat o The polymer chain is decomposed by a heated filament, and the resultant products are swept into and through a GC column. The separated decomposition products of the polymer emerge and are recorded. The pattern of this chromatogram or “pyrogram” distinguishes one polymer from another . The result is a pyrogram that is sufficiently detailed to reflect the chemical makeup of the binder Characterization of Pigments o The elements that constitute the nonorganic pigments of paints can be identified by a variety of techniques – emission spectroscopy, inductively coupled plasma (ICP), and X-ray spectroscopy The emission spectrograph can simultaneously detect 15-20 elements in most automobile paints ▯ Significance of Paint Evidence Significance of paint comparison was convincingly demonstrated from data gathered at the Centre of Forensic Science, Toronto, Canada o Paint chips randomly taken from 260 vehicles located in a local wreck yard were compared by color, layer structure, and when required, infrared spectroscopy o All were distinguishable except for one pair o In stats terms, there results signify that if a crime-scene paint sample and paint standard/reference sample removed from a suspects car compare by the previously discussed test, the odds against the crime-scene paint originating from another randomly chosen vehicle are approx. 33,000 to 1 o This type of evidence is bound to forge a strong link between the suspect care and the crime scene After automobiles the next most common paint analyses is that architectural paint o Architectural paint is CLASS evidence The computer database known as PDQ (Paint Data Query), allows an analyst to obtain information on paints related to automobile make, model and year o Contains such parameters as automotive paint layer colors, primer colors and binder composition Collection and Preservation of Paint Evidence Recovery of loose paint chips from a garment or from the road surface must be done with the utmost care to keep the paint chip intact May be picked up with tweezers or scooped up with a piece of pater o Paper druggist fold or glass vile If paint is speared or embedded into garments or objects, the investigator should not attempt to remove it, instead take the whole item and send it in When the transfer of paint occurs in hit-and-run situations, such as to the clothing of a pedestrian victim, uncontaminated standard/reference paint must always be collected form and undamaged area of the vehicle for comparison Important to take a sample from an area close to that of suspicion ▯ Forensic Analysis of Soil For forensic purposes, soil may be thought of as any disintegrated material, natural and/or artificial, that lies on or near the earth’s surface Forensic examination of soil is not only concerned with the analysis of naturally occurring rocks, minerals, vegetation and animal matter; it also encompasses the detection of such manufactured objects as glass, paint chips, asphalt, brick fragments, and cinders, who’s presence may impart soil with characteristics that make it unique to a particular location ▯ Significance of Soil Evidence The value of soil as evidence rests on its prevalence at crime scenes and its transferability between the scene and the criminal Thus, soil or dried mud found adhering to a suspect’s clothing or shows or to an automobile when compared to soil samples collected at the crime site, may link a suspect or objecting to the crime scene ▯ Forensic Examination of Soil Most can be differentiated by their gross appearance A side-by-side visual comparison of the color and texture of soil specimens is easy to perform and provides a sensitivity property for distinguishing soils that originate from different locations Soil is darker when wet, therefore all comparisons must be made when soil is dry Low-power microscopic examination of soil reveals the presence of plant and animal materials as well as artificial debris Further high-powered microscopic examination helps characterize minerals and rocks in earth materials A mineral is a naturally occurring crystal, and like any other crystal, its physical properties – color, shape density and refractive index— are used for identification o More than 2,200 minerals exist; most are so rare that forensic geologists usually encounter only about 20 of them Rocks and minerals not only are present in earth materials but also are used to manufacture a wide variety of industrial and commercial products ▯ Variations in Soil Ultimate forensic value of soil evidence depends on its uniqueness at the crime scene ▯ Collection and Preservation of Soil Evidence Standard/reference samples should be collected at various intervals within a 100 ft. radius of the crime scene Soil specimens also should be collected at all possible alibi locations that the suspect may have claimed In most cases only the top layer of soil is picked up during the commission of a crime, thus the standard/reference specimens must be removed from the surface Soil found on a suspect must be carefully preserved, if it is found adhering to an object, like a shoe, the entire object should be individual wrapped in paper and sent to the lab ▯ ▯ In 1901, Karl Landsteiner announced one of the most significant discovers of the 20 Century, the typing of blood ▯ Deoxyribonucleic acid (DNA): The molecules carrying the body’s genetic information; DNA is double stranded in the shape of a double helix ▯ The Nature of Blood The word blood actually refers to a highly complex mixture of cells, enzymes, proteins, and inorganic substances The fluid portion of blood is called plasma o Composed of principally of water and accounts for 55% of blood content Suspended in the plasma are solid materials consisting chiefly of cells, that is red blood cells (erythrocytes), white blood cells (leukocytes), and platelets o The solid portion of blood accounts for 45% of its content o Blood clots when a protein in the plasma known as fibrin traps and enmeshes the red blood cells o If one were to remove the clotted material, a pale yellowish liquid known as serum would be left ▯ Antigens and Antibodies Red blood cells transport oxygen from the lungs to the body tissues and in turn remove carbon monoxide from tissues by transporting it back to the lungs where it is exhaled Antigen: A substance, usually a protein, that stimulates the body to produce antibodies against it o More than 15 blood antigen systems have been identified to date; of these, the A-B-O and Rh system are the most important o Serum is important because it contains certain proteins known as antibodies Antibody: A protein that destroys or inactivates a specific antigen; antibodies are found in the blood serum Anti-A (A antigen) Anti-B (B antigen) Anti-D (D antigen) o The serum containing antibody is referred to as the antiserum, meaning a serum that reacts against something (antigens) Antiserum: Blood serum that contains specific antibodies o Antibodies are normally bivalent – that is, they have two reactive sites This means that each antibody can simultaneously be attached to antigens located on two different red blood cells This creates a vast network of cross-linked cells usually seen as clumping or agglutination Agglutination: The clumping together of red blood cells by the action of an antibody Blood Type Antigens on Red Antibodies in Serum Blood cells A A Anti-B B B Anti-A AB AB Neither anti-A nor anti-B O Neither A nor B Both anti-A and anti-B ▯ Blood Typing Serology: The study of antigen-antibody reactions The most widespread application of serology is the typing of whole blood for it’s A-B-O identity Type A blood is agglutinated by anti-A serum; type B blood is agglutinated by anti-B serum; type AB blood is agglutinated by both anti-A and
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