Forensic Notes on Evidence Classification - Part 2

Classifying evidence Is evidence direct or circumstantial? Direct evidence – establishes a fact eyewitness statements or confessions- NOTHING ELSE Circumstantial evidence – requires judge/jury to make indirect...

Classifying evidence Is evidence direct or circumstantial? Direct evidence – establishes a fact eyewitness statements or confessions- NOTHING ELSE Circumstantial evidence – requires judge/jury to make indirect judgement/inference about what happened e.g. fingerprint found at scene matching suspect If the fingerprint or hair found at crime scene matches that of the suspect, jurors may infer print/hair belongs to the defendant As fingerprint/hair was found at the scene, the defendant is linked to the scene Circumstantial evidence Often much more reliable than direct evidence eyewitnesses are notoriously poor at identifying suspects or recalling events (tend to interpret what happened) More objective – more likely to provide a reliable answer e.g. Eyewitnesses can be wrong as much as half the time Fingerprints/DNA evidence can (more often than not) accurately distinguish an individual from other 6-7 billion inhabitants of the planet. The Damilola Taylor Case November 27, 2000:, ten-year-old Damilola Taylor was stabbed to death on his way to a computer club meeting at his local library. A teenage girl came forward to give crucial evidence, under pressure from police and with the offer of a £50,000 reward, she claimed she had actually All forensics content 42  “witnessed” the incident from behind a parked car. Detectives concentrated the inquiry on the four youths. They eliminated the brothers Ricky and Danny Preddie, who had previously been prime suspects. In court, Bromley was quickly exposed as a greedy attention-seeker. LIMITATION OF ‘EYE WITNESS’ EVIDENCE!- Subsequent investigation of this case did identify blood and glass evidence which ultimately led to the Preddie brothers being convicted of manslaughter Further evidence classification How else can we classify evidence? Reconstructive evidence Any evidence that allows investigators to gain an understanding of the actions that took place at the scene Helps law enforcement officers gain better understanding at crime scene e.g. broken glass/fulcrum marks - may suggest point of entry e.g. footwear marks, blood spatters, bullet trajectory – may locate people in room/establish sequence of events All forensics content 43  Need to determine: who did what, where, when and how- could be fingerprints Associative evidence: Ties suspect to crime scene (or elsewhere) e.g. fingerprints, footwear marks, hair, fibres, blood, soil, etc can link a suspect to a scene. So… evidence can be: Direct or circumstantial Physical or biological Reconstructive and/or associative Hair DNA in follicle (with caution) - individual Assess pigments / shape - ethnicity, hair colour Determine species / breed of pet – secondary transfer Determine if hair was forcibly removed (violent crime) Chemical Analysis for e.g. illegal drugs (with caution Fibres and Hair Recovery: Pick off alien material, Tape-lift and retain on acetate sheet Analysis: Fibres and hair typically analysed by microscopies, with UV-VIS and IR spectroscopies to characterise pigments Glass Anaylsis of glass fragments Range of chemistry tests can be used to match or eliminate glass All forensics content 44  Colour, density, thickness using microscopy Refractive index measurements (RI) X Ray Fluorescence (elemental analysis) Laser Ablation ICP MS (inductively coupled plasma mass spectrometry) – starting to be used by the forensics industry (laser blasts atoms from the surface) UV-vis spectroscopy (“colour”) Need to consider how long glass fragments are likely to stay on any suspects Glass fragments can be collected with tweezers and placed in paper / plastic envelopes or bags Soil as evidence- biological evidence Bacterial DNA Pollen Particle size analysis Colour analysis Elemental (chemical analysis) Quartz Grain Texture analysis (quartz is a mineral in soils) Exclusionary technique : use of evidence to discredit alibi Class and Individual evidence Class Characteristics – not unique to particular object (place item of evidence into group of objects) Individual Characteristics – narrow down evidence to one person of very small group of individuals Evidence characteristics In general, all forms of evidence have class or individual characteristics. Class characteristics are not unique to a particular object but place the particular bit of evidence into a group of objects. All forensics content 45  Individual characteristics narrow down the evidence to a single, individual source. A piece of evidence may have more than one type of characteristic E.g. a blood stain Human : Class characteristic Blood type O- : Class characteristic DNA Profile : Individual characteristic Direct or Circumstantial= Hair/fibres Physical or Biological= Glass Reconstructive vs Associative= Soil Class or Individual characteristics= Firearms, tools, tyres, foorwear Firearms Examine (visually, weigh, measure, note characteristics) Test and compare with standards or control weapon Firing capability and bullets Firearms discharge Bullets All forensics content 46  Bullets recovered from scene may be compared to bullets obtained by test firing from suspect weapon. Class characteristics - grooves left by rifling in barrel: number, type and depth characteristic of weapon type Individual characteristics of gun barrel (hard) based upon minute imperfections during manufacture may be imparted on softer bullet Cartiridge Cases Often manufacturers’ identifying marks Individual characteristics of firearm may be revealed by marks left on relatively soft brass case and imprint of firing pin Fingerprints/DNA may have been left by anyone who has handled case GSR may be left in cartridge case. Gunshot residue Electron microscopy is used to locate particles Electron microscope uses a beam of electrons to generate an image of the particles and to test which elements are in the particles Limitatons of GSR as evidence Does not prove that the suspect fired a gun just in the vicinity Secondary transfer from arresting officers or police car Currently difficult to discriminate one type of GSR over another Pb-free ammunition – there is then no particle that is uniquely characteristic of GS The Crime Scene Purpose of scene examination: locate, identify, collect and preserve evidence Must be aware of what evidence can be collected All forensics content 47  what the evidential value is what examinations can be performed on evidence to further case to conclusion Investigating toolmarks- individual characterstics Tool mark – any impression, cut, gouge or abrasion on a surface (3- dimensional) Forced entry/physical injury- photos of wounds Causes both indentation into wood or UPVC or skin Tool usually of material harder than material struck Recognising tools used to commit crime Divided into three main types those that cut (e.g. saws) those that can be used as levers(e.g. jemmies, chisels) those used as striking tools(e.g. hammers and bats) Marks made by each likely to be different saws leave jagged edges, often linear repeating pattern (teeth) levers leave angled depressions (fulcrum marks) and splinters (broken surface) striking tools leave round, oval or square indentations Often possible to establish size/shape of weapon, but not necessarily specific weapon If suspect tool found Use to create number of test impressions Direct visual comparison with scene tool mark(s) Impress instrument into a soft medium (rubber-based compound) When making impression – important to imagine how tool might have been used at crime scene All forensics content 48  Recreate type of action as closely as possible Vary pressure and angle of attack (greatest chance of match) Recovering/Recording toolmarks at crime scenes Record evidence of mark using photography then cast /mould impression Large objects – e.g. door frame – may be possible to remove affected area by cutting it out Or mould/cast impression in-situ at crime scene If victim assaulted – necessary to photograph injury as soon as possible Changes as a result of bruising (later) may hide / reveal characteristics of weapon used Types of footwear impressions Two-dimensional footwear impressions When undersole of shoe encounters hard flat surface: When material adhering to sole transfers to surface (latent prints) Material (wet mud/blood) transferred from surface to sole (positive print) Leaving an impression in sand / soil/ dust etc (impressions in dust/wax polish) Often virtually impossible to detect with naked eye Contrast between footprints/background may be enhanced chemically and re-photographed Faint footwear impressions made in blood – spray with Luminol (to see chemiluminescence – a reaction leading to light emission) Useful first step – illuminate suspect area with high intensity light/oblique angle Footwear impressions (with scale) should always be photographed at crime scene Shots taken from directly above All forensics content 49  Various angles Position of footwear marks within context of crime scene View under conditions of complete darkness Use enhancement techniques used for fingerprints e.g. ninhydrin spray Three-dimensional footwear impressions Impressions from footwear into soft surfaces (often sand or soil) can be cast in the same way as tool marks Initially capture photographs Casting the print using plaster, gel or rubberised plastics (dental cement) Comparison to databases of flat images Direct comparisons to marks in foams / moulded Footwear marks as evidence Individual characteristics reconstructive Tyre marks All forensics content 50  Majority of major crimes involve use of a motor vehicle – some leave tyre marks Largely formed by tyre tread (part that normally makes road contact) Multitude of designs Important to record accurately by photography (and preserve Types of tyre marks- Latent tyre prints Invisible to naked eye Commonly found on smooth substrates Tyre print usually lifted with a black gel lift and photographed Chemical enhancement techniques may be used If latent tyre track contaminated: with grease apply Sudan Black; with protein use ninhydrin (goes purple) Visible tyre prints Visible tyre prints Positive - substance (e.g. blood/mud) picked up by tyre and deposited on comparatively uncontaminated surface Negative - tread of tyre removes material from substrate (vehicle driven over thin layer of snow) Plastic tyre prints Negative - formed when tread of tyre impressed into suitably soft substrate (deep snow/soft earth) Treatment of tyre marks First take photography Make casts (e.g. dental cement for impressions in soft earth/sand) Usually cast short portion of tyre mark (ca. 60 cm in length) All forensics content 51  Entire track may be recorded by sequential/overlapping photograph Scene prints may yield information about Identification of tyre type/manufacturer Make/year of manufacture Even motor vehicles on which tyres originally used May identify type of vehicle involved in incident (to narrow the field of the search) Tyre marks as evidence Circumstantial Physical Associative and reconstructive Class characteristics Tyre marks and tracking marks may, with expert help from a mechanic, be useful in identifying the vehicle type that made the marks Week 8- Post Mortem Interval Post-mortem Interval ‘Time of death’ 3 different times of death physiological; when the victim’s vital functions actually ceased legal; the time recorded on the death cetificate estimated; the time the pathologist estimates that death occured in criminal investigations, it’s rare for the physiological time of death to be accurately known, and its the estimated time of death that becomes important All forensics content 52  the time elapsed from the moment of death until a corpse is discovered is also known as the post-mortem interval (PMI) Why is this important? crucial for forensic investigators, especially when they are gathering evidence that can support or deny the stated actions of suspects in a crime exonerate a suspect or focus suspicion on them. can substantiate or refute witness and suspect statements one of the most important functions for the forensic pathologist can also come into play in civil situations insurance payments may depend on whether the insured indiviudal were alive at the time the policy went into effect or if he died before the policy expired Property inheritance can hinge on when the deceased actually died. distribution of property under a will might be affected by which partner died first Means of estimating PMI body temperature (algor mortis) rigidity (rigor mortis) lividity (livor mortis) stomach contents corneal cloudiness vitreous potassium level degree of putrefaction/decay insect activity different methods used according to the condition of the body/initial estimate of time of death PMI estimation from body temperature- Algor Mortis All forensics content 53  Means of estimating PMI most important and most commonly used of these are: body temperature rigor mortis lividity Body temperature (algor mortis) core temperature is measured from rectal temperature or liver temperautre a body starting at 37 degrees will drop on average by 1 degree per hour affected by envrionmental factors, including temperature of surroudings, layers of clothing there are more complex systems such as Hessenge Nomograms if measured under appropriate conditions, body temperature is potentially one of the best methods to estimate the time since death during the first 24 hours. Limitations only considered accurate during the pseudolinear section of cooling curce (not the initial plateau or as body temperature apporaches ambient) assumption is that the body temp at the time of death was within normal limits, 37.2 + 0.4 degrees (98.4 F) also assumed the enviornemntla temperature has reminaed constant over the postmortem interval Complicaing factors body mass, movement of air, humidity, clothing, water immersion Rigidity (rigor mortis) usually develops sequentially down the body, beggining in the muscles of the face (escpially those of the eyelids and lower jaw) and of the neck, then the trunk and upper lims and finally the lower limbs All forensics content 54  generally begins 3-4 hours after death, is fully established after 8-12 hours, reamined unchanged for up to 36 hours post mortem and then rigidity disappears after 2-3 days influencing factors/limitations temperature is a critical parameter heat accerlates rigor cold slows it down violent exercise prior to death may hasten the onset as well as disappearance of ridigity the more muscualr the subject, the greater the postmortem rigdity. on the other hand rigor mortis may be very moderate in children, emaciated people or the elderly rigidity may be delayed in some asphyxial deaths carbon monoxide poisoning, hanging state of rigor is genrally evaluate subjectly, using critea that vary from one athour/’expert’ to another Lividiity (livor mortis)- pooling becomes perceptible within 3-4 hours of death and progressively develops in surface area and colour intensity to attain its maximum degree 8-12 hours post-mortem After 12-15 hours, post-mortem pooling becomes ‘fixed’ and thus can no longer be displaced by external action (e.g. pressing skin). Colour then remains unchanged until masked by the generally darker discoloration resulting from putrefaction. Origin is the settling of red blood cells to lowest levelsin the vascular system after death- looks like bruising Does not occur in regions of the skin under pressure Can be a clue to whether body has been moved afterdeath Limitations All forensics content 55  Although present in almost all bodies (with the exception of those dying of massive haemorrhage), the time course of lividity exhibits considerable inter-subject variability probably to a greater extent than most other estimators of time of death. In most routine cases its estimation remains largely subjective Vitreous humor of eye linear increase in potassium level (liberated from retinal blood cells) as PMI increase of the different equestions proposed, the most popular are; Sturner’s formula; TSD = 7.14 [K+] - 39.1 Madea’s formula: TSD = 5.26 [K+] - 30.9 where TSD is the time since death (hours) [K+] is the potassoum concentration (mmol dm-3) advantage is that it may be carried out up to 5-7 days after death, whereas most other estimators (espicaillay body cooling) are useful within the first 24 hours limitations 95% confidence interval of the techniqye is large and reported values vary between authors levels can be strongly affected by the ambient temperate as well as by factors such as age at death, duration of agony etc at a given time, potassium concetration may differ significantly between each eye Other biochemical markers several investigated as estimators of time of death blood (electrolytes, glucose, lactic acid, hormones) vitreous markers (electrolytes, urea, pH) muscle marks (creatinine, enzymes) All forensics content 56  lung marks (surfactant phospholipids) many positive or negative correlations exist between the post mortem evolution of these marks and the time elapsed since death, but their relative coarseness make them unsuitable for pratical coursework Supravital Reactions (after death) an intermidiate period, beginning at brain death and lasting until cell activity has definetely ceased in the whole organism, is sometimes called the ‘supravital period’ becuase external stimuli (mechanical or electrical) applied to the corpse may induce life-mimicking, observable reactions none of the phenomena used have proved observale beyond 12-15 hours post-mortem Stomach contents of limited value immediately after death may be able to link undigested food to a time of death soon after eating that meal however, rate of digestions varies greatly with type of meal, individual, physical/emotional stress level Decomposition Putrefaction usual course of decomposition moist degeneration leading to liquefaction of soft tissues begins on 3/4th day in temp climates, possibily within hours in tropical symptoms: bloating of body, foul smelling odour being released, green discolouration of the body 5 stages of decomposition 1. inticial decay (up to 36-72 hours post mortem): the corpse still appears fresh externally but internally begins to decompose All forensics content 57  2. early putrefactoin or green putrefaction (up to 1 week post mortem): first visible on abdominal wall, gut bacteria proliferate and decompse red haemoglobin to greenish compounds staining the skin, swelling of body die to gas formation, superficial veins outline in red or green as bacteria grow through them. typical odour of decaying flesh 3. black putrefaction (up to 1 month post mortem): cadaver exhibits a flesh of creamy consistency with exposed parts turning black, espcially at the head and face. nails fall off, abdomen collapses as gases escape. odour of decay is at its maximum 4. butyric fermentation (up to 2 months post mortem): marked by a progressive drying of the cadaver and the occurance and proliferation of mould. the odour is becoming less offensice and becomes typically cheesy 5. dry decay, then skeletonisation (months to years): finally drying of the cdaver and progressive disappearnace of the remainign soft tissues. time- related chanfes affecting the reminas at this stage are slow compated with those of the preceding periods there is enormous and generally unpredictable intersubject variability. ambient temperate influences the rate of putrefaction to a major extent, other influencing factors include body corpulence there are also variants of the ‘classical’ succession of decomposition stages Decomposition mummification body may desiccate in dry, warm conditions, or cool dry places in draft of air mummified tissue dry, leathery and brown Entomology (insect action) after death, the tissues of animals become attractive to a large variety of insects and other invertebrates necrophagous species; invertebrates that feed on the corpse itself predators and parasites of the necrophagous species; these species do not feed directly on the corpse All forensics content 58  omnivorous species; invertbrates that feed both on the corpse and on the other arthropods present The only approach for estimating the time of death of a putrefied cadaver with some accuracy –in some cases, to within a few days Estimations of time of death require an accurate recognition of the species present on a corpse, or its surroundings, in their different stages of growth, together with an extensive knowledge of their specific rates of development A highly specialized role. Physical evidence Do not neglect other, potentially more precise ways of determining time of death Physical evidence (the ‘broken watch’ cliché) CCTV evidence Data from other digital devices....a growing source of evidence Week 9- Pathology Forensic Pathology What is it? Royal College of Pathologists states: ‘Forensic pathology is the discipline of pathology concerned with the investigation of deaths where there are medico-legal implications, for example, suspected homicides, death in custody and other complex medico-legal cases.’ Attendance at both the Crown Court and the coroner’s court is frequent, necessitating explaining medical issues to juries as well as relatives. Undertake opinion work for lawyers or other organisations- may be on behalf of a defendant on a murder charge or acting in civil proceedings. All forensics content 59  Role of the forensic pathologist: In a case of violent or unexplained death, the forensic pathologist will conduct a post-mortem (also known as an ‘autopsy’) and seek to answer some of all of the following questions. What was the cause of death? Who is this person? Why did this person die (murder, suicide, accident?) When did they die? (post mortem interval) Who was associated with the death? (are there any samples such as DNA that can be obtained?) Autopsy An autopsy (also known as a post-mortem examination or necropsy) is the examination of the body of a dead person and is performed primarily to determine the cause of death. Conducted in a way that minimises damage to features displayed in an open coffin Process 1. Begins with a complete external examination. The weight and height of the body are recorded, and identifying marks such as scars and tattoos are also recorded. 2. Look for evidence of blows, size, shape and location of wounds such as stab wounds or bullet entry points, or look for signs of asphyxia. 3. Internal examination begins with the creation of a Y or U-shaped incision from both shoulders joining over the sternum and continuing down to the pubic bone. 4. Skin and underlying tissues are then separated to expose the rib cage and abdominal cavity. The front of the rib cage is removed to expose the neck and chest organs. All forensics content 60  5. Following removal of the neck and chest organs, the abdominal organs are cut free. 6. The brain is removed by cutting the scalp, separating it from the underlying skull and pulling it forward. The top of the skull is removed using a vibrating saw, enabling the brain to be removed. 7. The spinal cord may also be taken by removing the anterior or posterior portion of the spinal column. 8. The organs are first examined by the pathologist to note any changes visible to the naked eye. Then, they are further dissected to reveal any abnormalities and tissue samples are taken for microscopy. 9. Organs may also be studied to see how external injuries connect to internal injuries, for example, bruising of the brain following a head injury or damage to the heart and blood vessels following a stabbing or shooting. 10. The stomach contents may provide clues to the time, circumstances or cause of death. The forensic pathologist will also look for microscopic changes in the tissues to support these observations. 11. The autopsy also provides an opportunity for other issues raised by the death to be addressed, such as the collection of trace evidence or determining the identity of the deceased, including: samples of DNA from under fingernails samples of semen from vaginal swabs GSR particles around a gunshot wound 12. The forensic pathologist may also collect and interpret toxicological analyses of body tissues and fluids to determine the chemical cause of accidental overdoses or deliberate poisonings. 13. As well as looking at how someone died, the forensic pathologist will determine why he or she died: Accident Natural causes Suicide Murder All forensics content 61  Sometimes, the outcome is inconclusive, and the cause of death remains undetermined. Identification of remains Forensic pathologists may also have to help identify the dead person, which can include looking at medical records and dental records, especially if the face has been mutilated. Identification evidence that may be taken includes: DNA Fingerprints Dental records Tattoos Skeletal information Identifying the cause of death Wounds Damage to the tissues of the body caused by mechanical force’, and includes: Punching Kicking Bite marks Knife wounds Strangling Shooting Drowning Poisoning Explosion Wounds can be classified. All forensics content 62  Forensic pathologist must record Nature of wound (i.e. classification) Length, width and depth of wound Position of wound in relation to anatomical landmarks In stab wounds and some vehicle-pedestrian injuries, the height of the wound above heel (ground) level should be recorded Closer analysis of some wounds (e.g. stabs) can provide information about the type of weapon used and how it was wielded Shape of wound Influenced by weapon type (e.g. knife, scissors) Influenced by movement in body (e.g. twist) Depth of wound Direction of wound Bruising/abrasion around wound Force of stabbing Other types of wound may lead more directly back to a perpetrator, or to clothing they may have been wearing Bite marks may link directly to teeth (and also give a site for DNA swabbing Bruising All forensics content 63  Bruise patterns may also reveal footwear marks in sufficient detail to identify shoe type (or other items such as belt buckles) May also have marks in blood present on the skin that can be enhanced Gunshot evidence Firearms Information that can be obtained includes: Type of weapon (recovery of bullets/fragments/pellets) Proximity of weapon (discharge pattern, gunshot residue [GSR]) Trajectory of projectile (from entry and exit wounds) Whether the wound is likely to have been self-inflicte Death from explosion injuries will vary according to proximity to explosion site May have fragments from multiple bodies intermingled Becomes important to identify them and link back to individual and their location primary blast injury (with blast wave itself), secondary blast injury (from missiles being propelled due to blast, teritary blast injured (impact with another object) Drowning Can be very difficult to prove at post-mortem, especially if body is not examined when relatively recently deceased Decomposition and prolonged immersion in water can mask some of the characteristics Plume of froth at mouth and nostrils Froth in trachea and bronchi Lungs over-distended Lungs may be generally waterlogged But those signs may also be absent All forensics content 64  Laboratory tests for drowning are not conclusive or universally agreed upon Diatom test: Diatoms are microscopic algae present in bodies of water; theoretically should never be present in a human unless they inhaled water Validity questionable because diatoms are present in soil and atmosphere, and samples are easily contaminated Absence of diatoms does not rule out drowning Paired cardiac electrolytes: In saltwater drowning, Na and Cl concentrations in right and left heart blood should be widely different Invalid if individual survived for a period of time or had significant CPR Cause of death Toxicological analysis required in cases where cause of death is suspected to be: Drugs Alcohol Poisoning Samples need to be taken, labelled and continuity of evidence established Blood Urine Vomit/stomach contents Faeces Liver and other organs Hair/nail clippings (particularly for heavy metal poisoning) Blood may be taken from the heart and femoral leg vein, often with sodium fluoride as preservative Testing may involve immunoassay, gas chromatography, or gas chromatography/mass spectrometry (GC/MS) Typical drugs and substances and that may undergo toxicology screening for a forensic toxicology report include: All forensics content 65  volatiles (e.g. chloroform, ethanol [alcohol], acetone, isopropanol, methanol and toluene) illicit drugs (e.g. heroin, cocaine, marijuana, PCP, methamphetamine) prescription drugs (e.g. benzodiazepines, opiates, amphetamines, barbiturates) over-the-counter substances (e.g. ibuprofen, acetaminophen) drug metabolites (breakdown products of drugs)- what the body turns the drug into Week 10- Scene Profiles- all biological evidence Forensic Palynology- study of pollen Provides evidence of location or of linkage between locations Each site - characteristic pollen ‘signature’ based on: Local flora Pollen releasing activity Characteristics of various pollen types Determination of Pollen Evidence Surface features (visible using microscopies) of pollen coat can be used diagnostically - number, shape, size, possession of apertures, furrows, pores, bladders, etc. Typical items or places where useful samples could be obtained include: Dirt, Mud or dust Hair or fur Fabric, packaging materials Nasal cavity or stomach of human remains All forensics content 66  Air filters, bank notes How can we use biological evidence? Suggesting point of origin for specimen - to link object or person to scene of crime/supporting an alibi Dating specimen or estimating time of death - determining how long a body could have been buried Providing evidence of the nature and/or location of death Helping to locate human remains Forensic Botany Suggesting point of origin for specimen - to link object or person to scene of crime/supporting an alibi Dating specimen or estimating time of death - determining how long a body could have been buried Providing evidence of the nature and/or location of death Basis of Forensic Botany Decaying vegetable matter in soil or mud can be transferred on skin, clothes, shoes, tools, vehicles Plant material from stems leaves, flowers Diatoms (such as algae from water) Spores and pollen grains To be useful, plant specimen should possess features that allow it to be identified to species level Must be specific to certain locations and/or times of year, either in isolation or in combination with other specimens Must persist well through time, being resistant to decomposition by natural and/or organic processes Recovery of plant material All forensics content 67  samples of whole flower or leaf must be recovered/maintained in the state found at the crime scene if dry, SOCO uses a brown paper sack; if damp, then keep damp in polyethylene bag during transport damp samples rot quickly so must be transported to a forensic science provider as soon as possible for examination by a qualified botanist Forensic Entomology Study of insects/other arthropods Medico-legal investigations - criminal aspects of legal system (dealing with necrophagous (of dead bodies) or carrion feeding insects infesting human remains) Urban investigations - insects that affect humans (living or dead) and immediate environment (may include civil and criminal components) Studies of stored product insects - commonly found in foodstuffs (civil and criminal components) Preferably a suitably qualified/experienced forensic entomologist How is Forensic Entomology applied to Scene Profiling? Forensic use of insects founded on two important features of their biology There are important feeders in all terrestrial environments, especially Diptera (flies) and Coleoptera (beetles) Rigid and repeatable life cycles - capacity for retrospective interpretation in forensic investigations For scene/event reconstruction it is essential to have: identification of the organisms proper understanding of insect biology and ecology understanding of life cycles - error in identification invalidates estimates of postmortem intervals appreciation of factors influencing timing of life cycle steps All forensics content 68  Different organisms are present in different areas - can be used therefore to provide reconstructive / associative evidence Insect development and life cycle (metamorphosis) Time spent in any life stage is a 'stadium' Each growth stage within a life stage is an 'instar' Exoskeleton (durable cuticle) shed at various points during growth (may allow forensic use long after insect's death) Appearance/duration of life stages is species-specific/influenced by environmental conditions Life cycle of flies True flies are holometabolous and undergo full metamorphosis Egg Larva - are necrophagous (feed directly on dead tissue) and can reduce corpse to bone and cartilage within 2 weeks (if conditions right) Pupa Adult Here it is essential to have temperature data Colonisation of Dead Bodies Above ground First colonisers may arrive within minutes of death Lay eggs (blowflies) or deposit maggots (flesh-flies) in natural orifices (eyes, mouth nostrils or in wounds) Joined later by houseflies (family Muscidae, order Diptera), and other insect groups (e.g. beetles) start to arrive while the number of fly larvae progressively decline Deep below ground (or submerged underwater) Bodies colonised by other invertebrate species (including insects) characteristic to environment All forensics content 69  In certain situations (e.g. body in sealed car boot) it may be impossible for any species to gain access to the body Post-Mortem Interval Early days after death - development of insects present can be used to estimate period of time elapsed since eggs laid State of decomposition of body also gives information Insects are cold blooded - rate of development affected by environmental conditions (especially temperature) If body found outside, climatic conditions (before/after approximate time of death) are needed to estimate time required for insect to reach stage of development Larvae usually form 'maggot-mass' and move around body collectively to feed (raises temperature of microenvironment esp. in second and third instar stages) After flies leave - succession of species arrive to colonise body, each associated with particular stage of decomposition, can be used to estimate post-mortem interval Factors affecting life cycle Rain and humidity levels in the area where the body is found can affect the time for insect development. Large amounts of rain - slower development due to a drop in temperature. Light rain or a very humid environment, by acting as an insulator, will permit a greater core temperature within the maggot mass, resulting in its faster development. Bodies exposed to large amounts of sunlight will heat up, giving the insects a warmer area to develop, reducing their development time. In contrast, bodies found in shaded areas will be cooler, and insects will require longer growth periods. If temperatures reach extreme levels of cold, insects instinctively know to prolong their development time - this increases the chance of survival and reproduction. All forensics content 70  Movement of Body After Death Insect species present on body discovered in rural area may include those usually associated with urban location Indicates person initially possibly killed in town/city and body subsequently dumped in countryside Knowledge of geographical distribution of insect species and life cycles is important in this case Collection of Entomological Samples Entomological samples taken from scene/later at autopsy must be collected, preserved and analysed correctly Live specimens should be collected to rear (take though growth cycle) through to adult stage to assist identification of species Third instar larvae ready to pupate leave body and bury themselves in ground nearby. Presumptive testing in forensics Benefits of presumptive testing Fast Easy to use and interpret Inexpensive Can be used in the field to establish which evidence to recover Can be used in laboratories as an initial screening test Most presumptive tests are chemical tests which result in a change in colour. These typically take 1-2 minutes to perform. What can Presumptive tests tell us Presumptive tests can not be used to provide a definitive answer due to potential false positives (other chemicals which create the same response All forensics content 71  as the target material). In general the results of a presumptive test are: The sample may be X The sample isn't Y Examples of presumptive tests Blood: Kastle-Meyer test (also known as the phenolphthalein test) Luminol test Drugs: Marquis test (opiates and amphetamines) Cobalt thiocyanate (Cocaine) Explosives: Griess test Confirmatory tests Confirmatory tests are used after presumptive test to 'confirm' the result Usually a fully accredited method (by UKAS) but will be slower, more involved and expensive than the presumptive test Examples include: Liquid chromatography mass spectrometry - DRUGS Gas chromatography - ACCELERANTS Gas chromatography mass spectrometry - EXPLOSIVES Presumptive Test Colour Test Drug analysis & toxicologist use traditional presumptive testing Most popular tests in these laboratories are; 1. Duquenois-Levine (for marijuana) 2. Cobalt thiocyanate (for cocaine and related drugs) 3. Marquis (for opium derivatives, amphetamines and other alkaloids) All forensics content 72  4. p-DMAB (p-dimethylaminobenzaldehde) for LSD The appearance of colour or the appearance of a colour change is evidence that a chemical reaction has occurred, and a simple colour change is often evidence of a complex chemical reaction Analysis of Seized Substances Colour tests (or chemical spot tests) provide toxicologists and drug analysts with one of the first tools for the presumptive identification of drugs and poisons Colour and/or spot tests indication of the content of any particular item Advantages & disadvantages of colour tests: advantage that unskilled operators can use them as field tests, with the obvious need for follow-up analyses in the laboratory. Simple, rapid and inexpensive to perform Can be performed in the field Tests are not selective - follow up lab tests Reagents can be used for TLC (thin layer chromatography) development Use positive and negative Colour test target: types of compounds and functional groups. Drugs of interest in forensic chemistry are characterised by a relatively small number of functional groups, most important are; Phenols Aromatic rings Basic nitrogen i.e. primary, secondary, tertiary amines Since many drugs have more than one active site, colour testing is more complicated than the simple identification of the drugs functional group 1. Specific Tests: For some substances, the colour reaction with a particular chemical reagent may be quite specific All forensics content 73  2. Class of compounds More common for the colour to be produced by a class of compounds. 3. Drawbacks Compounds that do not fall into the class may also give colours. For some of the tests, the colour reactions can be correlated with certain aspects of the chemical structure of a compound or group of compounds. (may not always be attributed to these factors ) It follows that colour tests are only an indication of the presence of a compound or class of compounds and that all tests must be confirmed by more specific methods. This is especially important in forensic cases! Summary Presumptive tests are: Fast Cheap Easy to interpret Useful to direct search / investigation Presumptive tests are not: Accurate (high number false positives / negatives) Sensitive (potential false negatives) Definitive (require confirmatory test) Week 11- The Court, Evidence and Likelihood What is forensic science? All forensics content 74  From crime scene to court: pathway of evidence Forensic services in the UK Forensic providers are responsible for the analysis/ interpretation/ evaluation of evidence Public or private entities that offer forensic services All forensics content 75  They can be commissioned by both prosecution and defence What are the forensic providers? They are usually organised in units: Evidence Collection Unit Chemistry Unit Biology Unit Firearms Unit Document Examination Unit Photography Unit E-crime Unit Toxicology Unit Latent Fingerprint Unit Polygraph Unit (truthfulness of statements to police) Voiceprint Analysis Unit Forensic Pathology Forensic Anthropology Forensic Entomology Forensic Psychiatry Forensic Odontology Forensic Engineering Cybertechnology Current forensic provider organisations 1. Police (scientific support or in-house forensic provision) Varies in different parts of the UK 2. Government Providers Defence Science and Technology Laboratory (DSTL) All forensics content 76  incorporating Home. Office Centre for Applied Science and Technology (CAST) National Crime Agency (NCA) 3. Private companies and independent forensic practitioners Police provision of forensic services Police provide in-house forensic services across the UK Exact provision varies between forces but generally includes: Scene examination Photography and imaging Fingerprint development Fingerprint analysis Forensic management (outsourcing testing to other labs) Police Scotland (Formed in 2013) In-house digital forensic services (E-crime unit) Scottish Police Services Authority has expertise in all other forensic disciplines Police Service of Northern Ireland (PSNI) Scientific Support Branch In-house digital forensic services (E-crime unit) Forensic Science Agency of Northern Ireland (FSNI) forensic advice and scientific expertise including explosives analysis Government provided forensic services Defence science and technology laboratory Agency of UK Ministry of Defence Formed July 2001 and since 2018 includes support to UK Home office All forensics content 77  Team of scientists providing expert advice, innovation and frontline support on: Contraband detection (illicit material includes people/stowaways, money, drugs, explosives, weapons and chemical, biological, radiological and nuclear material) Crime investigation, prevention and community safety Identity assurance Protective security Public order Surveillance UK Forensic explosives laboratory, firearms, ballistics Identification of chemical/biological warfare agent National Crime Agency (formerly Serious Organised Crime Agency Tackles serious and organised crimes Supply forensics to MI5 (Military Intelligence, Section 5, British security service) MI6 (SIS, the Secret Intelligence Service, British foreign intelligence service) In relation to: class A drugs people smuggling and human trafficking major gun crime fraud computer crime and money laundering Private forensic providers All forensics content 78  Eurofins Forensic Services Incorporates part of what was Laboratory of the Government Chemist Currently the largest private sector provider Analysis of: drugs DNA ecological samples (insects, pollen) questioned documents toxicological samples (ante-mortem and post-mortem) mobile phones, computers gunshot residue and firearms Independent forensic providers (practitioners) Small-scale Specialized in a particular service (e.g. questioned documents analysis_ authenticity, origin, signature, handwriting) Work alone or as a part of a private practise Often employed by defence (defendant = person accused in a court of law) May be called to appear in court to give expert witness testimon → Main customers of private forensic service providers 1. Regional police forces in England and Wales 2. Other police forces (British Transport Police, Ministry of Defence Police) 3. Crown Prosecution Service (CPS) 4. HM Revenue and Customs 5. Lawyers (defence or prosecution) All forensics content 79  In court - defence and prosecution Can also undertake forensic science work commissioned by defence lawyers. provided that for the case concerned they had not also undertaken work at the request of the police/prosecution Forensic science regulator All forensic providers that report to the Criminal Justice System (CJS) must have a required level of quality standards The Forensic Science Regulator ensures that the provision of forensic science services across the criminal justice system is subject to an appropriate regime of scientific quality standards. Responsibilities involve: identifying the requirement for new or improved quality standards leading on the development of new standards where necessary, providing advice and guidance so that providers of forensic science services can demonstrate compliance with common standards Quality standards are set out in “The Codes” (can be downloaded from: www.gov.uk) UKAS (National accreditation body) How do we know that a forensic provider compiles with the quality standards set out in the Codes? UKAS. All UK forensic providers should be inspected by UKASto ensure they meet the standard required. Function: “to assess, against internationally agreed standards, organisations that provide forensic certification, testing, inspection and calibration services” UKAS is responsible for determine integrity and competence of organisations There is a UKAS database to hold the status of each forensic provider based on ISO standards All forensics content 80  ISO standards (International Organisation for Standardisation) ISO 17025 laboratory-based provisions include: Laboratory personnel possess knowledge, skills and abilities to carry out tasks assigned Secure storage conditions for evidential samples (i.e. to avoid any contamination, deterioration or loss of evidence) Full validation of all technical procedures (protocols, SOP = standard operating procedures) Proper use, maintenance and calibration of the equipment used in the forensic laboratory Maintenance of a chain of custody (written documentation of history) Keeping records of actions undertaken Presentation of results compliant with ISO 17025 requirements Court Process What happens next? The Crown Prosecution Service All forensics content 81  In England and Wales the Crown Prosecution Service (CPS) is the chief agency working on behalf of the state responsible for the prosecution of criminal offenses Created by Prosecution Offences Act (1985) Roles of CPS: Advises police (possibility of prosecution) Reviewing cases submitted by the police Oversee the progression of cases/determine any changes Prepares case for court Presents case at court Prosecution lawyers (CPS) must prove guilt (beyond reasonable doubt Structure of the courts All forensics content 82  Overview of a criminal ilitigation procedure and appeal system All forensics content 83  Trial procedure of criminal cases The Verdict Jury/magistrates retires to deliberate case and agree verdict All forensics content 84  (≥ 2hrs 10 minutes – often longer) Possible Verdicts: ‘guilty’or ‘not guilty’(England, Wales, NI) additional‘not proven’(Scotland) For a verdict of guilty (crown court) (majority verdict): 10 out of 12 jurors must agree (England, Wales, NI) 8 out of 15 (Scotland) If ‘hung jury’ – cannot make decision: Trial will conclude, albeit without a verdict. Defendant has neither been acquitted or convicted CPS must determine whether they will have a retrial The Principle of adversarial justice The criminal justice system in England and Wales is based on the Principle of adversarial justice Prosecution has to prove that defendant is guilty beyond reasonable doubt (the burden of proof) must be able to present sufficient admissible evidence to convince either the magistrate(s) or the members of the jury of the guilt of the defendant All forensics content 85