Forensic Science Notes - Week 1-2 PDF

All forensics content Week 1- Introduction and Evidence Direct evidence - establishes facts - Eyewitness testimony or Confessions (ONLY). Although this establishes facts, the accuracy of this may be...

All forensics content Week 1- Introduction and Evidence Direct evidence - establishes facts - Eyewitness testimony or Confessions (ONLY). Although this establishes facts, the accuracy of this may be questionable (either deliberately or accidentally) Circumstantial - requires interpretation - most evidence falls into this category. This can be really strong evidence (eg DNA) but still be circumstantial. locards exchange principle- ‘every contact leaves a trace’ eye witness testimony limitations- intentional blindness and change blindness role of forensic science 1. has a crime been committed? (scientific examination of evidence, mo) 2. who is responsible? (fingerprints, footmarks, DNA evidence) 3. is the suspect responsible? (check corroboration of evidence e.g. DNA, clothing, footwear) 4. can a prosecution be supported? (evidence collected by investigators is examined by Crown Prosceution Service (CPS), CPS advises police on whether a prosecution might be successful having reviewed the case) history of forensic science first forensic lab in USA (1923). first private forensic lab in USA (1929) USA is 1920s- gang warfare surrouded control of illegal alcohol trade All forensics content 1  st valentines day massacre 7 of one of chiacgos lead mob bosses’s men were killed real police arrived found corpses had been shot many times (recovered 7 shell casings) and bullets from bodies comparison microscopy Dr Calvin Goddard identified the casings (45 calibre) as being from Thompson sub-machine gun - used by police in the Chicago area Then, using newly developed comparison microscope, tested casings from Thompsons belonging to police. None connected with police weapons - suspicion fell on Capone and 2 Thompsons were later found in the home of one of his gang members (confirmed as linked to shootings). Impressed by Goddard's work, Chicago business leaders financed the establishment of a private crime laboratory in Chicago. Chicago Police Department, which was rife with corruption at that time. Week 2- Crimes Scenes Crime scenes Crime scene; location where an illegal act took place area where most of physical evidence is retrieved by trained law enforcement personnel by crime scene investigators (SOCO’s, CSIs- based at police stations or by (rare circumstances) forensic scientists (who are usually laboratory based)- example 7/11 bombing in London Primary crime scenes; where the crime actually took place All forensics content 2  not necessarily be location to where officers were called normally yield more usable evidence than secondary crime scene there will be only ONE primary crime scene may be one event where there are multiple offences committed and some of those offences may be committed elsewhere so they’re primary crime scenes for individual offences but for the overall crime there will only be 1 primary crime scene Secondary crime scenes; a location related to the crime but not where the actual crime took place sometimes this is the only scene the investigators know about there can be many secondary crime scenes Role of Investigators investigation process: crime committed → crime reported → decision to investigate → evidence preserved and recovered → evidence anaylsis and conclusions → decision to prosecute → present evidence in court Scene examination process: CSI tasked → preserve scene → assess scene → record and document scene → identify items of evidential value → record and gather items CSI role confirm crime committed → scene preservation → ID key evidence → record all evidence → recover all evidence → package and store evidnce → brief OIC/SIO → prepare statements → present evidence in court Crime types All forensics content 3  forensics is expensive for minor crimes they have to make the decision as to items to send for analysis- which items are most likely to lead or support a conviction as opposed to when there’s a major crime involved where you send as much as you can because it is high profile and important- a separate budget will be found to cover it For the First officer attending a scene (depending on whether it is a major or volume crime) will govern the steps that they take major crime 1. preservation of life 2. protection of property- e.g. make sure a fire is put out 3. maintenance of order- can we protect the rest of the public? can we set up a cordon? can we ensure people are pushed back to a safe area? law and order is preserved 4. preserving evidence 5. apprehension of offender volume crime 1. deal with victims 2. obtain witness information 3. preserve evidence 4. call for CSI 4. offer crime prevention advice initial tasks All forensics content 4  ensure health and safety set up cordons and rendezvous point- prevent people from accessing the crime scene set up crime scene and attendance log Dynamic risk assessment scene envirionment, biological hazards and chemical hazards done at crime scene done by taking very brief notes at to how you deal with things making sure you can deal with the scene as you need to after a dynamic risk assessment you need to set up cordons inner cordon: the forensic investigators outer cordon: are the pieces of police tape, accompanied by a police officer- at front and back of crime scene control access preserve the scene- maintain the continuity of evidence- not changed from arrival to analysis in laboratory provide safety- makes sure people are at a safe distance cordon safety distances? very different from case of car bombing to a suspicious package like a briefcase or a bomb declared at the gherkin 100m- briefcase/bag 300m- vehicle 700m- building how to protect yourself when going inside a cordon (use the dynamic risk assessment) All forensics content 5  Scene Preservation is required to prevent; loss of evidence destruction of evidence contamination of evidence movement of evidence how to we protect the scene other than actually stopping people going in? protection of evidence inside cordon establish a Common Approach Path (CAP)- everyone who attends the scene walks in the exact same steps, follows the same path into a scene because it minimises their impact initial preservation of evidence stepping plates- stop us touching the ground evidence markers covers Managing evidence in a scene: Zoning and Searches Zoning a crime scene crime scene is mentally broken down into zones physical zones used in major crime scene (two barrier tapes) All forensics content 6  each zone searched carefully for evidence before moving on Zone search- can be used to find a standard pattern e.g. a car may always be searched in the same order Complex crime scenes; zoning large scenes zoning in a large and complex scene is especially important all the debris and evidence from any one one is collected, sorted and sifted together making it easier to identify items from similar location e.g. the Manchester bombing Search Methods- for zoning large scenes- breaks up the monotony = increases focus the zone pattern the person in charge spilts the crime scene into sectors and a team member is given an area of the crime scene each. the area can also be further broken down into sub-areas to help record where specific items were found. the team then swap and recover the areas to ensure no evidence has been missed strip/parallel search pattern quite straight forward. the members of the team form a line and walk all at the same speed from one end of the crime scene to the other grid method similar to parallel but done from different bearings on a 90 degree angle. e.g. if the search was from the left to right (West to East) it would then be done from the bottom to top (South to North) outward spiral investigators start at the centre of the scene and work there way outward in a spiral to the edge inward spiral All forensics content 7  opposite to outward spiral, investigators start at edge of the scene and walk to the centre in a spiral Recovering evidence: Evidence Packaging Preservation of evidence damage: correct packaging minimise handling degradation inappropriate storage high humidity or temperature continuity integrity contamination packaging storage handling (tools, gloves, PPE) cross contamination segregation (personnel, items) Principles of evidence preservation Locard’s Principle- two way transfer of trace evidence type of surface type of transferred material pressure of contact duration of contact All forensics content 8  the more unique evidence is to the scene or individual the greater the likelihood it will be accepted as evidence e.g. making contamination is coming from the right places make sure secondary transfer of material doesn’t come from poor procedures incorrect or poor packaging but instead comes from the interaction of the perpetrator with the item Crime scene items; items of interest can be; item of property piece of trace evidence image/photograph body fluid swab fingerprint or footwear lift cast recovery of items items of interest are; photographed in situ (on site/scene)- if serious or major crime recorded on a list with full description number of items recorded item assigned exhibit reference number sometimes assigned a barcode importance of packaging: securing evidence- no tampering preserve evidence- robust prevent contamination- uncompromised facilitate tracking number/barcode- URN All forensics content 9  ensure continuity- label packaging decisions; must consider health and safety size will contents be contained? will contact be adequately preserved? does the item require freezing? will the item puncture or rip packaging? does the item need to be seen?- e.g. a gun types of packaging: paper bag plastic bag cardboard box (e.g. guns- with see through part) evidence bags (not suitable for vapours) paint tin (arson evidence) knife tube (sharp items)- then put in evidence bag how would you pack? clothes (evidence bag or nylon bag)- each item in separate bag fire damaged book (nylon bag- protect vapours) cast of a footprint (fragile- don’t want it rocking around- cardboard box with other material inside to stop in moving around gun (cardboard box) needle (sharps containers) knife (sharps containers- if blood is present you don’t want containers with absorbent material on the end) complex evidence- a blow up car or unblown up car (wrap it up with a tarpaulin to ship back to lab to protect car from elements) All forensics content 10  Which packaging would you use? brown papers bags- all items of clothing or fabric unless wet (use bags/cool box/ice packs for transfer to laboratory for drying damp items must be dried (carefully) as soon as possible to prevent mould damage Volatile Organic Compounds (VOCs)? accelerants (often used in arson) are typically VOCs must avoid polyethylene bags (VOCs diffuse through the walls) Nylon bags or metal flame tins for non biological volatile liquids (inner push-top air seal/secondary screw top outer seal) Continuity and Labelling CJA Label (Criminal Justice Act, 1967)- PACE must be attached to packaging of every piece of forensic evidence recovered at crime scene provides accurate record for court, detailing; what is in sample where it was recovered from when it was recovered who recovered it Labelling Unique identifier given to particular sample at particular scene All forensics content 11  CSI job number initials of person who recovered sample number of a sample in sequence of recovery e.g. 12345/MB/7 the label also shows signatures of everyone who has handled sample since recovery, including the SOCO (chain of continuity of evidence) label details must identify exhibit and account for movement from scene to lab. to court must log every movement of evidence signatures indicate who has transported it/examined it ensures continuity of evidence and custody thereof labelling is very important all sides are sealed/all edges secured with tamper-proof tape (mark with initials and date) if packaging is compromised- no examination should take place label info must match logbook label attacked with adhesive tape initialled over tape/packaging information on label name(s) of suspect(s) if known with date(s) of birth exact identity of the evidence (e.g 103 white jumper) exact location where it was found date when it was collected signature of person who collected it Week 3- Documenting a scene All forensics content 12  ENFSI Best practice European network of Forensic Science Investigators have developed a manual of best practice for scene investigations. 5.6.2 The crime scene examination must be comprehensively documented. Documentation may include hand written notes, voice recorded notes, taking information directly onto computer, sketches and diagrams, photographs, video recordings, etc. 5.6.3 A contemporaneous record should be made, at the time of seizure of items from the scene describing the exact locations from where the items were recovered. It is also helpful to mark this location on a sketch/plan of the scene or Crime scene sketches Detailed sketches with accurate measurements showing the dimensions of the scene, locations of all objects identified. Must be done at scene but can be used for secondary sketches afterwards. Objects are measured from 2 fixed locations Add key to label items North should be shown to understand orentiations Photography photographing the crime scene for court purposes 'Three Shot Rule' (long range, medium range, close up) Photographs should be taken: before scene is disturbed Photographs should be taken to document evidence found in situ (at the site prior to recovery) after the addition of a measurement scale after evidence has been collected Must be correctly exposed All forensics content 13  Have maximum possible depth of field (more things in focus) Have an accurate perspective (lens distortion) An evidence number must also be visible (preferably with case number etc) Note: Some evidence numbers have rulers on them and others do not Pictures should be taken from a 90 degree angle where possible quality: avoid motion blur- tripod or stablisation hold resolution the more pixels the better the image measured in pixels per inch (PPI) dots per inch (DPI) fingerprint capture required at least 500 DPI we can never have more DPI than in the original image image size more pixels, more bits per pixel, more tonal values= better image= great image size Photographing the crime scene: rule of 3 long range shot= enables viewer to locate the exhibit in relation to general surroundings medium range shot= shows clearly exhibit and anything immediately around it close up= shows exhibit in situ (should fill most of frame- with measurement scale. close up photos with exhibit made more visible. final photo of location where exhibit has been removed role of digital photgraphy All forensics content 14  chain of custody must be maintained the photo must be identified must have confidence that the image has not been modified specialist digital systems in place to facilitate the downloading of images from cameras/cards preserving integrity legal process acceptance around 2002 image continuity image captured= master and working copy= CD storage, serve storage, remains secured and untouched until court, used to produce hard copy images, used for image enhancments guidance for using digital images in CJS Ref: Practice Advice on Police Use of Digital Images - NPIA 2007 Must be an audit trail & full continuity No captured images can be deleted Use one memory card for each job Images stored on WORM media e.g. CD-R or server Create exhibited Master CD and securely store Retain for statutory period then destroy Complete the audit trail image security enhancements detected by verification software enhancements cause tonal values to change where the alteration has been made scanning your scene 3d laser scans are now widely available to help document a crime scene. As with most new innovations they are not replacing what has traditionally been All forensics content 15  done by adding to it Documentation of scenes and evidence Preparing documentation for court If SOCO and scientist attend scene - each produces separate forensic report for court Scientist writes crime scene report Details scene in descriptive format - point of entry, environmental conditions, date, time, location and position of bloodstains, etc. Photography logs SOCO produces statement of facts for court Indicates what has been collected and unique reference numbers/description of each type of evidence collected SOCO is not entitled to give his/her opinion in court unlike forensic scientist Crime scene reports While at a crime scene, it is imperative that a CSI maintain a detailed record of actions, observations, information, and evidence recovered. Important part of both the investigation and intelligence gathering. The style and layout of a crime scene report varies greatly between agencies. A crime scene report states the identifies and explains the place where something such as; an accident occurred. They are used in legal cases such as claims and police reports. What is in a crime scene report? The datum point (when was the scene attended) Photographs and list of photos taken (including evidence found) All forensics content 16  Observations of local conditions (weather, light etc) Location sketches (you could include Google map overview, maybe show where photographs were taken, lines of sight & measurements) Relevant Location features e.g. road signs & markings Any other relevant information e.g. results of finger print development and other analyses conducted at the scene A crime scene report should include the following details: case number and agency details of crime or incident address or scene details of CSI details of victims) details of first officers) attending date and time of incident, or time frame date and times CSI arrived and departed modus operandi and other details This should be as detailed as possible and include the following: description of the scene; actions and apparent actions taken by offender(s); point and method of entry to the scene; items moved by offender(s); items stolen by offender(s); items from scene not taken by offender(s); items abandoned by offenders(s) Care should be taken that a crime scene report remains an investigative tool and does not become solely a means of gathering statistical information All forensics content 17  that does not assist the investigative process. Photo log For each photograph some or all of the following details are required: shutter speed film speed lens number and size, e.g., 55 mm aperture distance from camera to object in question and distance from reference points direction of photograph, i.e., north photographic placards and what they indicate Statements Statements are sometimes prepared in lieu of attending court Should contain all the information needed to communicate what you saw, what you found, how you dealt with the scene and what you believe was going on (based on the recovered evidence) Who attended these scenes? What were the roles of those people at each scene? What did you find at the scene How did you analyse it ? What did it tell you ? In your professional opinion - what had occurred at the scenes? If there were additional crime scenes linked to this crime these should be mentioned All forensics content 18  What is a Statement? Written record of activities of SOCO at a scene of crime - under the 1967 Criminal Justice Act this may later be presented to a court Must contain signed declaration: contents are, true and any evidence provided that is known or believed to be untrue may lead to prosecution Usually written by SOCO at request of Crown Prosecution Service (CPS) Criminal Procedures and Investigation Act (1996) - both prosecution and defence must disclose any material that may undermine the case Defence may apply for court order to access information that prosecution may possess that could assist defence's case All evidence, including SOCO's paperwork, can be required to be produced before court of law What must a statement contain? Individual must identifying his/her role list relevant qualifications and professional memberships Detail who employs the individual Date/time he/she attended address(s) Describe location(s) that individual attended Detail photographs taken, samples recovered, fingerprint examination conducted When examination of crime scene was concluded What was done with photos, forensic samples, fingerprints recovered from scene (e.g. secure storage, processing or analysis) Item examination To help ensure that contemporaneous notes are kept, most forensic providers will have a standard form to help ensure: Consistency Details Description All forensics content 19  Procedure Reviewed Exact form detail will depend on the Forensic Service Providers (FSP) accreditation and standard operating procedures (SOPs) Evidence recovery The first step to the investigation of any forensic exhibit is the physical examination of the exhibit and the retrieval of any evidential material. There are various steps to this process. PREPARATION OF EXHIBIT 1. When you receive your exhibit, examine the packaging to check it is secure and intact and look for any signs of tampering. If any tears or marks are observed then this should be noted on the General Examination Record (GER) and photographs taken of any damage. 2. The packaging should cut open. Do NOT go into the packaging through the original seal. Always cut a new hole elsewhere on the package 3. Carefully remove the item from the evidence bag and place it either directly onto a clean bench or onto a piece of clean bench roll or brown paper. If any debris falls from the item during this process, collect it and put it into a Petri dish or grip seal bag, label and seal. This should be noted in the GER. PRELIMINARY EXAMINATION 1. If the orientation of the item is significant to the case, for example clothing received inside out, then a photograph of the item should be taken in the condition it was received. Carefully lay the item flat on the bench and recover any obvious extraneous material, for example glass fragments or debris. 1. If the item is to be examined for glass evidence, then any fragments should be collected and packaged carefully, when the item is first examined. This is done to ensure that as much evidence is collected as possible as this can be lost rapidly from exhibits once the packaging has been opened. 2. Examine the item with the naked eye and a light source if available, looking for obvious stains and damage. All forensics content 20  3. Describe the item and record its condition on the GER Note-taking and repacking 1. Notes should be prepared contemporaneously. You will have instructions relating to specific evidence types for guidance on requirements of examination and note taking. 2. Diagrams should be labelled, and any significant measurements taken and added to your diagrams. 3. A scale or ruler must be placed in every photograph taken. 4. If the evidence is damp. it must be dried before it is repackaged. 5. Once the item is dry, carefully replace it in the original packaging and reseal using thick sticky tape and signature seals. a. sign two white sticky labels, b. place them over the cut you have made in the packaging, c. using thick sellotape, tape over the 2 signature labels 6. Sign the CJA continuity label (not the 'opened by' label, this is for recording when the packaging is opened at court or the police station) on the outside of the packaging and store the exhibit. 7. Always record the location of the exhibit in your case file. In this case you will need to hand the exhibit back to the academic or technician and ask them to sign the continuity on the back of your case file Handling evidence Invalidating evidence damage or contamination of evidence could results in it being invalid. must be handled carefully in accordance in procedures with appropriate tools with correct PPE by approved persons locards principle All forensics content 21  PPE PPE (personal protective equipment) is designed to protect you from the crime scene but also the crime scene from you Making sure you have the right PPE means the evidence you are recovering is more likely to remain undamaged Is one pair enough ? Week 4- Documents, Fraud and Forgery What is a document? something that contains information normally refers to paper, but can also include messages etc written on walls, boards or even bodies information can be considered as occurring at two levels superficial- writing, typewriting, printing deeper level- identity of writer, source of writing or printing, altercations Why do examine documents? to demonstrate their authenticity to identify the author or the origin of the document to establish whether the document has been subjected to altercation to obtain additional, contextual information (e.g. hidden messages) Documents examination Which? handwriting (cursive/printing) and signatures All forensics content 22  typewriters, photocopiers, laser printers, ink-jet printers, fax machines rubber stamps, price markers, label makers printing processes ink, pencil, paper What/How? Altercations, additions, erasures, obliterations indentation detection and/or message decipherment sequence determination- what came first? did somebody handle the document after it was written or before? was this letter written before that letter? physical matching Authenticity Proving authenticity of official documents is often aided by the deliberate inclusion of security features that make them more difficult to forge or alter e.g. passports, driving licenses, banknotes many of these features are designed to be revealed when viewed under specialised conditions of lighting watermarks thickness/density variations in paper produced by passing it through rollers that emboss an image onto the pulp roll something over the top of the paper when it’s still damp to change the density. that means that light can either be easily transmitted or less easily transmitted. and there’s either a positive or negative image depending on how you’ve done it becomes visible when viewed using transmitted light fluorescent markers All forensics content 23  inorganic pigments and organic dyes both used to print features that fluoresce under ultraviolet light traditional inorganic pigments based on zinc sulfide and zinc cadmium sulfide doped (activated) with silver, copper, or manganese. The activator types and amount used determines the colour of the fluorescence (but there are toxicity issues) modern pigments are composed of a microcrystalline host (or matrix) based on oxides, sulphides and oxysulfides of ‘rare earth’ elements, and aluminate of ‘alkali earth’ metals with an activator organic dyes with UV fluorescence include those related to fluorescein, coumarin pyrene, rhodamine. holograms multiplayer designs that change appearance depending on viewing angle authenticity can be checked using controlled illumination and varying illumination angle bichromatic inks (when viewed at different angles, these inks change colour, they are available with 2 or 3 colour-shift effects and can provide security without a reader) disappearing inks anti-stokes features absorption of longer wavelength radiation (e.g. IR) resulting in emission of shorter wavelengths (e.g. green) very common in nature marks are illuminated using infrared light- then we get to see it in the visible spectrum infrared reflection many printing inks based on organic dyes do not reflect or absorb near infrared radiation they therefore ‘disappear’ when viewed using infrared light wavelengths All forensics content 24  can be used in combination with inks that remain visible in the NIR to print patterns that present a different appearance to that viewed under white light optically variable pigments (OVPs) designs change colour depending on viewing angle OVPs are multi-layer films of semi-transparent reflector (metals) and ‘dielectric’ materials the centre ‘inner reflector’ layer is usually aluminium How do we analyse a document? Document examination equipment Commercial equipment available allows rapid examination of secrity features of documents allows illumination/irradiation with UV, visible and infrared wavelengths has reflected, transmitted, fluorescence lighting modes has variable lighting angles and cross-polarisation Printed/handwritten documents is the type of ink and printing method used consistent with the supposed origin? (diameter of nip, correct shade of black) is the type of paper used consistent with the supposed origin? have any altercations been made? Ink analysis simple liquid chromatography techniques still highly effective in discrimination between inks or visible similar appearance Paper analysis visible/microstructural analysis simple measurements (grams per square metre, permeability) All forensics content 25  more advanced analysis of ‘fillers’ using analytical techniques or microscopy Handwriting analysis comparative methods used to establish if questioned document has been written by a claimed author comparison of words from known text with equivalents from questioned documents also analysis of other features within written text (can also be applied to analysis of disguised writing) when you sign your signature you do it very quickly, not putting much pressure onto the paper, but when tracing you apply an even force and pressure as you take longer can be detected by lighting techniques and microscopy to reveal where pen has been lifted from paper, and underlying indentations Detections of altercations Pigments in some inks fluoresce in the infrared region of the spectrum when illuminated with light in the visible region of the spectrum this can be used to reveal obliterated text this may also reveal where different inks have been used to alter text in documents same effect can be useful in viewing text that has become illegible, for example by fading or erasure by water damage infrared fluorescent pigments that are invisible to the eye may still remain in situ Infrared reflection can also be used to reveal obliterated text and document alterations in this case it is the difference between inks that reveal were change have been made Ultraviolet fluorescence All forensics content 26  also be useful in detecting erasures, for example when writing has been removed using solvents, bleachers or simple fading before being overwritten Additional contextual information can we determine some thing about the character of the writer? “Graphology’ first proposed in the 1600s to try to link writing style to authors characters- less scientific basis (not really used now) is any additional information present on the document? indented writing from previous letters/messages (accidental)- tested using ESDA (Electrostatic document examination secret writing (deliberate) can we tell what order inks were deposited? can we tell which printed a document was produced from? Invisible writing often associated with spies and agents, many basic ‘secret inks’ such as lemon juice can be revealed by gentle heating, or ultraviolet fluorescence many complex chemistries developed for inks that will only be revealed by a specific, chemically compatible developer Prisoners, Lover and Spies- the story of invisible ink from Herodotus to al-Quaeda. Kirstie Macrackis, 2015 Order of deposition microscopy used to determine which link line has been deposited first may also be important to determine whether text or images were present before a document was handled Advanced analytical techniques can play a role (SIMS- don’t need to know this just that the technique plays a role) Printer identification All forensics content 27  the type of printer (digital or otherwise) can often be determined form a close analysis of printed text, but is it possible to link a document to a single printer many inkjet printers use black ink but much of the time when you’re printing black you are actually printing in multi colours to make up a composite black can tell different inks from each other- canon vs knock offs (formulated differently) when you zoom in under a microscope you can see the individual colours making up the black itself can be achieved for certain types of printer, in particular colour printers Printer ‘steganography’ can be used to trace the exact printer that produced the document by analysis of yellow dot patterns left by colour printers MG21 ‘Request for Analysis Form police use it to document the submission of evidence to a lab for examincation provides details on the crime being investigated and the details of who is handling the case provides details for the lab on the background of the case Details of an individuals who have been identified and the points of law being examined additional info and dates item details, serial numbers etc forms may differ from force to force GER- ‘General Examination Record’ All forensics content 28  Forms used by forensic examiners when an item of evidence is being examined Every organisation will probably have their own version of this type of form- adapted to the specific requirements of that laboratory to help ensure that contemporaneous notes are kept, most forensic providers will have a standard form to help ensure consistency details description- can include sketches procedure reviewed continuation pages available exact form detail will depend on the forensic service providers (FSP) accreditation and standard operating procedures (SOPs) Week 5- Fingerprints fingerprints are collected under controlled conditions fingermarks is one accidentally left at a crime scene Bertillonage 1883 Proposed ‘Anthropometry’ as means of identification (re-named Bertillonage) Based on observation that adult bones (>20yrs) tend not to grow substantially Measure major bones- accurate and unique method of identification Strict system of measurement (France) Officers measured/catalogued 11 different features: size of head, arms, legs, feet, hands, fingers etc. Simple numerical system allowed measurements to be matched All forensics content 29  Quickly became internationally adopt (for around 10 years) Winter 1884- 241 repeat offenders identified 1903 “West Brother’s” case eventually showed fingerprint evidence to be more reliable End of Bertillonage These are the mugshots of 2 individuals both called William West They were both sent to Leavenworth at the same time After much confusion the staff understood they have the same name and physical characteristics but are 2 different people They did however have different fingerprints What are fingerprints? Patterns of ridges on the fingers and palms help us to grip things general ridge patterns determined by genetics, although fine detail determined by local conditions in wom (pressure, flow of fluid etc) therefore, indetical twins will tend to have similar patterns on each fingers, but their fingerprints differ Fingerprint patterns don’t naturally change through someone’s life, and they are one of the last features to be lost from decomposing skin eccrine sweat glands are the only type of gland found in these areas Fingerprint patterns Three basic pattern types defined for fingerprints All forensics content 30  Arches 5% of all fingerprints Plain arch- simplest (ridges flow from one side to other, rising smoothly in centre like wave) Tented arch- intermediate between arch and loop (central upthrusting ridge(s) meeting at 90%) are latent- these require some means of development or enhancement to make them visible enhancement involves using any technique that exploits differences between the properties (chemical, physical or otherwise) of the fingermark and the surface, providing sufficient contrast for them to be readily distinguished Current enhancement techniques comparative tests required to establish which are most effective All forensics content 37  some only effective on porous surfaces, some only effective on non-porous surfaes selection will depend on consideration of surface, type of mark and environment it has been exposed to (the ‘Triangle of Interaction) ‘Fingerprint manual advises on which technique to use, for which surface and in what order Fingermark enhancement research has resulted in a wide range of techniques becoming readily available for chemically and/or physically enhancing latent marks these processes utilise any techniques that can provide contrast between fingermark ridges and background chemical reactions yielding coloured or fluorescent products (e.g. ninhydrin, DFO) dyeing of fingermark constituents by stains polymerisation reaction catalysed by fingermark constituents selective deposition of material influenced by physical/chemical properties of fingermark examples include; superglue fuming nihydrin spray magnetic powder dusting vacuum metal deposition powder suspensions FIngermark imaging White light examination use of light in different modes to enhance mark and suppress background oblique lighting All forensics content 38  specular lighting dark field illumination generally utilising the optical properties of fingerprint and background to give contrast Colour filtration Can use coloured filters in combination with white light, both to increase contrast between the developed mark and the background and to suppress the effect of distracting coloured backgrounds contrast enhancements and background suppression Fluorescence examination Fluorescence can be used to produce contrast where the fingermark fluoresces and the background does not. Required long wave UV light source to promote fluorescence More recently, portable lasers and LEDs produced limitation of UV light- it may degrade biological material Optical processes uses radiation outside the visible region of the spectrum, for example ultraviolet reflection (but caution required for DNA) on glossy, porous surfaces absorption dominates infrared reflection is particularly useful for revealing makrs on patterned, multi-coloured backgrounds Fingermarks imaging Digital imaging has presented new options and made other aspects of imaging easier: Real time imaging outside the visible spectrum Processing of captured images Ability to rapidly see whether required detail has been captured in image All forensics content 39  Fingerprint Matching Fingerprint comparison- the UK’s national database info includes fingerprints palm prints scene of crime marks incorporates ink prints and scanned prints hold 8.3 million individuals ten-prints, 1.9 million unidentified marks, 8.8 million palm prints, 173,260 palm marks, 3,293 serious crime marks, 38,179 scene of crime identifications over the last 6 months makes 85,000 matchs with data recovered from crime scene per year verified over 1.5 million arestee indentifications per year How does it work? Every person arrested in England, Scotland and Wales has their fingerprints and palm prints taken and entered into database. DNA and mug-shot photographs also obtained. In England and Wales fingerprint images are only removed in special circumstances once suspect has been charged, but Scotland removes records on acquittal. Technology includes Automated Fingerprint Identification System (AFIS) search engine and two principal databases - one contains the national fingerprint (tenprint) database with over 8.3 million identity records and a second holding unidentified crime scene marks. Ridge details fingermarks are encoded The coded ridge detail is searched against the IDENT1 database All forensics content 40  The database returns images of the first 15 marks that it considers most closely match the coded sequence The expert reviews the images and selects which they feel is likely to be a match If they find sufficient features in agreement, the conclude it is an identification This conclusion is then independently verified by two other experts Summary- fingerprints Fingerprints are still most common form of identification evidence collected by police institutions Fingerprints can be used to check the identity of a suspect Matching to a database Fingerprints can be used to determine whether someone was at a crime scene / handled an item of evidence Matching to a fingermark Marks must be developed, illuminated and imaged by chem lab to provide images for fingerprint examiner Most fingerprint reagents involve wet chemicals although more sophisticated techniques emerging When developing a fingermark care must be taken to do the analysis: Taking account of the surface and environmental exposure Non-destructively Cheaply Week 7- Trace Evidence All forensics content 41