An application of Science to Law, Science to Criminal Justice The analysis of physical, chemical and biological evidence Forensic Medicine deals with crimes involving a human body (Murder, rape, assault) Forensic science enables us to reconstruct the past sequence of events.Forensic science can link a suspect to a crime scene.Examples of forensic evidences are: Fibers (clothes, carpet) Hair Blood If newsprint Shoe print Paint Forensic evidence can distinguish been murder and suicide.
Locator Exchange Principle by Proof.
Edmond Locator “Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him. Not only his fingerprints or footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects. All of these and more, bear mute witness against him. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. Physical evidence cannot be wrong, it cannot perjure itself, it cannot be wholly absent.
Only human failure to find it, study and understand it, can diminish its value. Every Contact leaves a Trace Case Study: Burglar severed a finger on razor wire while breaking into a builder’s yard was caught by police when he went to hospital for treatment. Earliest forensics lab in US is in Austria, LISA in LAP. Singapore forensic lab is set up in 1960 by Proof Chaos Tweeze Change, now part of HAS. In a Forensic Science Lab, you can find: . Physical Science Licit a. Identification and comparison of evidence b. Chemical tests c. Spectroscopy d. Microscopy Drugs, glass, paint, explosives, soil… E. 2.
Biology Unit a. Hair b. Plants 3. DNA Lab DNA analysis a. 4. Firearms Unit a. Guns b. Bullets c. Cartridge cases . Firearm damage 5. Documents Unit a. Handwriting b. Printing Paper d. Ink 6. Photography Jinni a. Record of evidence b. Presentation Toxicology – drugs and poisons in body fluids and organs Latent Fingerprints – using chemical means to making them visible Polygraph – or lie detector Vectoring -? analysis of voices Psychiatric Profiling -? What can we tell about the criminal from the way they commit the crime Computer Forensics and Electronic Forensics -? What can be learnt from deleted data?
How can other electronic trails be followed? Forensic Engineering – Examine the engine emerging aspects of a building or object Forensic Entomology – Using insects to provide information Forensic Geology – Soil Analysis on mineral content and chemistry. Soil in different countries have individualistic composition. This composition helps to narrow down to a region Of the world. Forensic Anthropology – Examination of skeletal remains Facial Reconstruction – If you have the skull, can you tell what the face looks like?
Forensic Demonology – using teeth to provide information such as identification of victims remains or criminal Identification: physical objects Biological properties Chemical properties/constituents We collect as many evidence as we can on scene. These evidences have class characteristics that can put an object in a certain class or group like brand of shoe, type of fiber or type of bullet. Individualizing: Narrowing the class to one, Attaining more information from evidences from a crime scene.
Physical objects: Manufacturer, serial number, fingerprints Chemicals: Trace elements and impurities Biological samples: Blood type and DNA analysis Then we do comparison and associate the evidence to the crime scene and the criminal. After which, reconstruction to understand the sequence of past events and Re-enactment Chapter 2: Spectroscopy and the Structure of Atoms Elements are the basic materials consisting of 93 natural basics and many more artificial ones. Elements can neither be created nor destroyed.
Paper Cellulose consists of C, H, O CA Carbon Dioxide CA and Water H2O Human Body consists of C, H, O, N, P, S, Ca, An, K, Fee… DDCD, H2O, N oxides, P oxides, S oxides, Ca oxides or hydroxides… Teeth contains Au or Hag C] Au or Hag oxides Analysis: Which elements are present? E. G. Suspected lead or mercury poisoning but are these metals present in the body regardless of their chemical form? Toxicology. E. G. FUN analysis. How much of these elements were present in the Poltroon bones? Time of Death. What is it made of? How can we identify the elements present in an object?
Bulk composition (what is it mostly made of? )e. G. Bullets are mostly lead. Trace impurities (what is a small part of it made or? ) e. G. Bullets have silver and antimony Chemical tests can be done to identify these elements and chemical tests have the following characteristics: Large amounts Of sample is needed Destructive Subjected to interference Fast process Easy to do Simple equipment White light consists of all colors. In the early 19th century, black bands observed in the solar spectrum. Different spectroscopic techniques use different frequencies of light.
The different frequencies of light interact differently with the molecules. Structure of Atom: Tiny, dense, positively charged core called nucleus where nearly all mass is concentrated with electrons circulating at some distance. Founded by Ernest Rutherford. Nielsen Boor found that electrons are restricted to specific energy levels, therefore atoms don’t destroy themselves due to electrostatic attraction. Electrons can jump to higher energy levels by absorbing energy. Electrons can release energy when they drop to a lower level. The frequency of the electromagnetic radiation emitted or absorbed is proportional to LEE De
Broglie equation: E = HP (Constant x frequency of electrons) Absorption Spectroscopy is when electron jump to higher energy levels, energy IS absorbed. A drop in graph for short interval of time. Emission Spectroscopy is when electron drops to lower energy levels, energy is given out. A sharp spike in graph. Flame tests for metals: if a metal salt is introduced to a flame, a characteristic color is produced. Energy of the flame excites electrons in the atoms and light is emitted as the atoms drop back to ground state.Sodium: Orange Barium & Copper: Green Calcium & Lithium: Red Potassium: Lilac
Atomic Absorption Spectrometer (AS): Advantages: Fast Specific Sensitive Small sample size Disadvantages: Element by element Neutron Activation Analysis (*ANA) Non-destructive but needs a nuclear reactor Changes the nature of element Each emitted gamma ray is at dif. Energy level. Microscopy Scanning Electron Microscope – Energy Dispersive X-ray fluorescence (SEEM- DEG)* Non-destructive analysis looking at core electrons Use the electron beam of the microscope to eject core electrons Ejecting a core electron creates a vacancy. When a higher energy electron drops to fill vacancy, a characteristic X-ray is emitted
CASE STUDY: Napoleon. Analysis of hair samples by Neutron Activation Analysis shows arsenic. Paint used for one of Napoleon’s wallpaper is Chisel’s Green which consists of copper arsenate. SEEM-DEG shows presence of arsenic. When copper arsenate reacts with mold, arsenic gas is produced. CASE STUDY: Kennedy Assassination 22nd Novo 1 963 Analysis of bullets fragments by Neutron Activation Analysis (ANA) shows the content of Antimony and Silver. You are What You Eat! Bones consists of calcium phosphate in a protein matrix. Calcium is derived from the diet.. Other metals may also be incorporated if they are present in diet.
Relative abundance of trace elements in bone can indicate geographical origin: Strontium, copper and lead. Chapter 3: Time Of Death Alger Morris: After death, muscles relax, body is limp and starts to cool down. The rate at which body temperature cools depends on size of body, location, clothing, weather. Different parts of the body cools at different rates. E. G. Brain cools faster than liver. General rule is -1 to 1. Degrees Fahrenheit However, note that the body may start to warm up after 2 days due to start of putrefaction Rigor Morris: Lactic acid in the muscles causes tension up to 36 hours after death E. . Jaws (errs), arms (4-errs), legs(8-1 Oh RSI), whole body (10-rush) Liver Morris (Color of the body): Also known as Postmortem lividly: the black and blue disconsolation of the skin of a cadaver, resulting from an accumulation of degenerated blood in subcutaneous vessels. Hypothesis: poor or stagnant circulation in a dependent part of the body or an organ. Settling of red blood cells due to gravity (post mortem lividly, hypothesis 0-ours) Disconsolation in lower parts. Parts on the ground not affected due to compression of capillaries (contact flattening) *Has the body been moved?
If a body has been moved, he calculation of the body may not give the correct approximation of the time of death. *Take note that CO poisoning has similar symptoms as Liver Morris, CO poisoning results in cherry pink calculation due to the carbon monoxide-hemoglobin complex Physiological Changes in the body after Death. The average core temperature of a body is 9. Degree Fahrenheit. Postmortem interval = 99. 6/1. 5 (general rule). Other indicators that can estimate the time of death are: Kit levels in ocular fluid (vitreous humor) which increase after death Stomach and intestine contents (time of last meal).
A stomach empties its contents in about 2 hours. Look at other objects such as watches or mobile phone records and CATV. Putrefaction This is the process when your micro-organisms start to eat you after death. This produces gases and characteristic smells. The rate of putrefaction depends heavily on local factors such as temperature and also drug use. Forensic Entomology (Using insects) Insects can arrive and lay eggs as early as minis after death. In order to estimate the time of death, the species, life cycle, local conditions of that particular insect must be known. Live maggots are collected from the corpse and rear until adulthood.
After which, back calculate age and determine pieces. Skeletal Remains A forensic pathologist or anthropologist will use astrology, the study of bones, to find out as much as possible about the identity of a skeleton or collection of bones. Sometimes they rely on skeletal radiology, the study of bones through x rays or fluorescence (light-emission) to help make the identification. No fluorescence indicates that the skeletal remains is 1 00 years old or more. FUN analysis As time passes, the organic components of bone (mostly fats and proteins) are lost primarily through bacterial action.
Since these components contain nitrogen, there is a progressive loss of that element. At the same time, percolating ground water deposits trace amounts of fluorine and other elements, such as uranium, into the bone. Bone nitrogen content decreases with age (proteins breakdown). Bone fluoride and uranium increases with age. Fresh bones should contain 4% of nitrogen and 0% fluoride and uranium. Therefore, FUN analysis is useful for comparing samples from the same burial grounds/sites. Carbon-14 Dating The natural amount of ICC, a radioactive isotope formed in atmosphere by cosmic rays, is constant and living things have this proportion of ICC.
Radioactive atoms decay at a predicable rate and only half of the atoms will eve decayed in arrears. Hence measuring the amount of ICC allows estimation of time of death through back calculation. This method is not accurate for <400years because amount of decay is too small. Moss (vegetation) accelerates the decay of 14C. Algor mortis, Rigor mortis, Livor mortis, state of putrefaction, entomology, FUN analysis, fluorescence, 14C dating are all techniques to estimate time of death but they are subjected to errors. Analysis of Compounds Different compounds move at different speeds through an absorbent (stationary phase).
Components can be detected as they get to the end. Movement is due to the flow of a liquid or gas (mobile phase). Thin Layer Chromatography (TTL) Colored compounds are visible to the eye while others can be made visible through chemical staining or UP light. TTL is a presumptive test, it is unable to distinguish all the different compounds in the sample and only provides 2 answers: NO or MAYBE. Gas Chromatography (GO) GO can only be used if the unknown sample passes TTL. GO depends on the rate of which the compound moves at different temperatures. GO is still not accurate enough.
High Performance Liquid Chromatography (HAPLY) HAPLY is similar to GO, but uses a liquid mobile phase. The graph result of HAPLY has very sharp and narrow peaks which are highly distinguishable to determine the different compounds in an unknown sample accurately. HAPLY GO For both methods: Efficient, highly selective and widely applicable Only a small amount of sample is needed Non-destructive to the sample Readily adapted to quantitative analysis Has high resolution Advantages of HAPLY: Can accommodate non-volatile and thermally unstable samples Advantages of GO: Simple and inexpensive equipment Rapid process How do we tell what compound is it?
By comparison of chromatography of authentic samples By spectroscopy By spectrometry Infra-red Spectroscopy Based on molecular vibrations (stretching and bending of chemical bonds) Stretching frequency depends on masses involved and stiffness of the bond The graph of infra-red spectroscopy has 2 parts, before 1 500 wave number and after 1500 wave number Before 1500-6000 wave number shows the characteristics Of the class of compounds, but not Of individual compound After 1500 – 600 wave number shows Characteristic of individual compound like a molecular fingerprint Mass Spectrometry Measures the molecular weight of the sample. . Sample is introduced into a vacuum box 2. Sample is bombarded with electrons, leaving only positively-charged ions 3. Ions are accelerated by high voltages (100 – 1 0,VIVO), ions is deflected into magnetic field to detectors, measuring the mass of the molecule. *Know how to calculate molecular weight Some molecules will break up in the spectrometer known as Fragmentation. Gas Chromatography – Mass Spectrometry (GO-MS) Another hyphenated tech unique.