Forensic Field Skills Flashcards
What did Locard believe?
No matter where a criminal goes or what he does, he will leave something behind and take something away.
What is Locard’s principle?
Every contact leaves a trace
What did Karl Landsteiner do?
He discovered human blood groups in 1901.
What did Revenstorf do?
In 1904 he claimed that diatoms could be used to distinguish ante-mortem from post-mortem drowning.
Where was the first British forensics lab established?
Hendon
When was the FBI established and by whom?
1905, Theodore Roosevelt
When did Watson and Crick discover the structure of DNA?
1953
When were dental records first used for ID?
1940s
What does AFIS stand for?
Automated fingerprint identification system
Who first used Gas chromotography - mass spectrometry for forensic use?
Zoro and Hadley in 1976
Who discovered a method of identifying individuals from DNA?
Sir Alec Jeffreys
When was DNA profiling first used to solve a crime?
1986 (Colin Pitchfork)
When did world’s first national DNA database in the UK commence operations?
1995
What is the CSI effect?
The unrealistic expectation of jurors wanting to see DNA, fingerprints and trace evidence.
When did the forensic science service launch the UK’s first online footwear coding and detection management system?
2007
What does the CSI effect not consider?
- Not all scenes are evidence-rich2. Not all techniques/equipment seen on TV really exists.3. Evidence may be compromised
What is a crime scene?
Any location where a criminal offence has occurred or any place that contains physical evidence.
What is the golden rule of crime scene investigation/management?
Never touch, change or alter anything until it has been identified, documented and measured…when a body or article has been moved, it can never be restored to its original position.
Exceptions to the golden rule:
- If the potential exists that an item of evidence could be used to cause harm/death to someone at the scene.2. If the potential exists for an item/evidence to be lost/contaminated or destroyed.
What is the role of the first response officer?
Approach -> Preserve life -> Arrest perpetrators -> Safety issues -> Secure and protect -> Identify witnesses.
What is the meaning of secure?
Secure is to “close access”.
What is the meaning of protect?
To “deny access”
What measures can be taken to secure a scene?
- Tape2. Cones3. Police officers4. Vehicles5. Fences6. Walls7. Buildings8. Any impermeable landmark
What is an inner cordon?
The area of the incident and crime scene.
What is the outer cordon?
Seals off an extensive, surrounding the inner cordon. All access and exit points will be controlled by police. The control/command vehicles of emergency services will be positioned between the inner and outer cordons.
What is a common approach path?
The only entrance to a scene.
Who to deny access to?
Anyone who is not there to record, collect or preserve evidence.
Generic roles of the first response officer
- Access scene2. Establish communication3. Emergency services deployed4. Commence scene log5. Protect any transient evidence6. Try to identify deceased and suspects7. Gather details of potential witnesses8. Conduct preliminary risk assessments
The role of the first supervisory officer
- Reviews first officers works2. Sets perimeter of scene/cordon/CAP
Category A crime
A major crime of major public concern
Category B crime
Routine major crime when offender is unknown.
Category C crime
A major crime when the identity of the offender is apparent.
Key players at major crime scenes
- First response police officer2. Uniform supervision3. DS4. Scientific support coordinator5. Crime scene manager6. Crime scene investigation team7. Force medical examiner8. Other specialised personnel
Specialised personnel roles…
Are UNBIASED. They also seek to exclude the innocent and assist prosecution of guilty
What is the role of a Forensic pathologist?
- Conducts post mortems2. Find cause, manner and time of death3. Authorised by Home Office4. Medical degree +2 yrs training
What does a ballistics expert do?
Analyse bullets, firearms, ammunition and impacts to establish the firearm used at a scene.
What does a Forensic scientist do?
- Assess 2. Examine3. Interpret4. Identify5. Liaise with SS personnel6. Report7. Court recognised expert
What is forensic entomology?
The use of insects and their arthropod relatives that inhabit decomposing remains to aid legal investigations.
What does a forensic entomologist do?
- Attend the scene and collect insect and weather data2. Use the data to estimate PMI3. Expertise is location specific.
What is forensic Anthropology?
It serves the investigative and judicial communities by analysing human remains for medicolegal purposes.
What does a forensic anthropologist do?
- Attend scene to recover remains and soil samples.2. Full exam in lab3. Help establish ID, cause of death and social/habitual characteristics.
What does a senior investigating officer do?
- Manages the enquiry2. Maintains policy documents in relation to all actions completed.3. Chairs strategy meetings
What does a scientific support coordinator do?
- Designated in major/multiple scenes2. Liaises with scene managers, specialist forensic service providers and SIO3. Attends strategy meetings4. Controls budget for forensic examinations
What does a crime scene manager do?
- Manages crime scene team2. Allocates tasks3. Liaises with crime scene coordinator/SIO4. Carries out initial and final walkthrough5. Responsible for health and safety of team6. Manages contamination, continuity issues and integrity of scene.
What is the overall protocol of the forensic team?
- Assess scene2. Examine scene3. Record detail4. Disclose everything5. Forward evidence6. Advise and communicate
What does an exhibits officer do?
- Responsible for secure storage of all forensic exhibits.2. Attends scenes, searches and post mortems3. Ensures continuity of exhibits4. Prioritises exhibits5. Responsible for health and safety issues in relation to the handling of chemically treated exhibits6. Ensures exhibits are available at court (attends)7. Ensures all exhibits have been disclosed to defence.
List required personnel at a crime scene team.
- Crime scene manager2. Forensic scientist3. Photographer4. People to retrieve forensic samples5. Fingerprint experts6. Exhibits officer
What details are required in the exhibits book?
- Entry number (Initials and #)2. Description of property/item3. Witness reference no.4. Court exhibit no.5. Where found6. Found by7. Time and date found
Why is PPE worn at the crime scene?
To avoid contamination of evidence from the person collecting it.
What are stepping plates used for?
To avoid damaging evidence on the floor such as footprints.
Name the four search techniques.
- Parallel2. Grid3. Zone4. Spiral
What is trace evidence?
Any object that can establish that a crime has been committed or can link a crime and its victim or the perpetrator.
What are the different types of glass with examples?
- Sheet - sheds/greenhouses2. Float - windows3. Pattern - privacy4. Toughened - glazed doors/tables5. Laminated - windscreens6. Wired - fire doors7. Container - bottles/glasses
How is contamination avoided?
Avoid situations whereby same officer deals with victim and suspectSuspect’s exhibits and other exhibits must be kept apart*Exhibits must be packaged and sealed immediately
How does contamination occur?
Introducing evidence to the scene that was not originally therePoor examination and handling of exhibitsPoor packaging of exhibitsUsing contaminated equipment
What are the effects of contamination?
You are the custodians of evidence. If the evidence is not collected in the correct way, the science can be thrown out of court
What are the three main considerations for exhibits?
- Integrity2. Continuity3. Packaging and Handling
What aspects must an exhibit have once collected?
- A form of signature seal- Continuity of exhibit label- A backup label- Clean, sterile containers/packaging is always used
What 10 pieces of information must the exhibit label contain?
- Police force2. Station code3. Description of item4. Where found (full address)5. Where found (within the address)6. Date found7. Time found8. Exhibits reference9. Signature of recovering officer10. Signatures of all subsequent people that handle the exhibit
What must be considered when handling exhibits?
- Always wear gloves- Take the packaging to the exhibit - not the other way round- Do not let the object come into contact with you or any other contaminated area- Deal with each exhibit independently- Do not leave unsealed packaging around the office
How many skeletons did Wingate Todd collect and when?
2600 individuals between 1912 and 1938
What is a documented collection of skeletons?
A set of skeletons with pre-known sex and age
How many skeletons did Robert Terry and Mildred Trotter collect and when?
1636 individuals between 1914 and 1965
Why are four fields used in Anthropology in North America?
It provides a holistic approach to the study of humans
What are the four fields in Anthropology in North America?
- Physical- Archaeology- Social - Linguistics
Where were the first international forensic anthropology teams working?
Argentina, Guatemala, PHR, and ICTY
What is the official name for the ‘body farm’ and where is it based?
Anthropological Research Facility, Tennessee, Knoxville
What British associations are there for forensic anthroplogy?
BAFA (British Association for Forensic Anthropology) within BAHID (British Association for Human Identification)
What tasks are there for a forensic anthropologist?
- Locate and recover remains- Anthropological analysis including:* Establishing the biological profile* Trauma analysis * Estimation of the post mortem interval (PMI)* Identification
What kind of cases do forensic anthropologists work on?
- Fresh bodies: aging and trauma analysis- Aging the living (young offenders)- Cases of historical interest- Mass disasters (Disaster Victim Identification (DVI) teams)- War crimes and crimes against humanity
What are three things archaeological and law enforcement techniques employed for?
- Site location- Excavation- Documentation
What five techniques can be used to determine site location?
- Aerial photography- Vegitation changes- Ground Penetrating Radar (GPR)- Soil changes- Probing
What is stratigraphy?
The study of soil layers (strata)
What is the law of superposition?
Strata that are younger will be deposited on top of strata that are older, given normal conditions of decomposition
Can the exact same approach be used for all graves?
No. Each grave is different and so each requires a different approach
What will affect the law of superposition?
The creation of a burial pit as it will disturb the layers of soil
Why should care be taken when excavating?
Excavation is a destructive process and we need the maximum amount of evidence recovered, so it is vital to document each step.
Heavy machinery is used until…
the burial level is reached.
What should be used to excavate when the remains are found?
Small hand tools.
What must be first observed of the scene?
Orientation of body/ relationship to artifacts.
What must take places at all stages of the investigation?
documentation - notes/sketches/photography.
What must the soil first undergo?
Screening.
What questions will an anthropologist ask first?
- Is the material bone?2. Is it human bone?3. How many individuals?4. How long ago?5. Are they of forensic significance?6. What is the individuals profile?7. Are there any unique anatomical features/pathologies?8. Cause of death?
Why can smaller fragments be hard to identify whether bone or not?
Lack diagnostic features.
Why is there confusion between human and non-human bone?
- Absence of a cranium2. Not familiar with human skeleton and variation.
How can small fragments be identified?
Microscopy or chemical analysis.
What are common differences between human and non-human bone?
- Size, shape, texture2. Histological differences
How many cases are reported to be be non-human bones?
30%
What is used to determine the MNI?
Anatomical relationship, duplication, size consistency and joint articulation.
What does MNI stand for?
Minimum number of individuals.
Sex determination…
- Only reliable in adults2. Skull & Pelvis (morphological methods)3. Rest of skeleton (metric methods)4. DNA last resort (subadults & fragments)
When determining age, why are different methods required for adults and subadults?
Development & degeneration
How are subadults aged?
- Long bone lengths2. Tooth formation3. Tooth eruption4. Epiphyseal union
How are adults aged?
- Pubic symphysis2. Auricular surface3. Sternal rib ends4. Cranial suture closure5. Dental attrition6. Histological methods
How is ancestry determined?
Caucosoid, Negroid, Mongoloid. Europe, Africa, Asia
Which ancestry traits are centered on the skull?
- Nasal area2. Zygomatic bones3. Jaws4. TeethOther postcranial elements can be used but not as reliable.
What is the cause of mixed traits?
Mixed ancestry.
How can we estimate stature?
- Correlation between bone length and stature2. Development of regression equations from individuals of known stature3. Lower limb long bones are more reliable4. Population specific - correct formulae must be used.
What other useful form of identification can be found on the bone?
Pathologies leave traces on skeleton which can be traced with medical histories, narrowing down the field.
What is PMI?
Post-mortem interval.
What is time since death based on?
The principals of forensic taphonomy: 1. Associated artefacts, smell, texture and presence of soft tissues.2. Chemical analysis3. Ultraviolet light (questionable)4. Other disciplines such as entomology and botany.
What possible causes of death are there?
- Blunt force trauma2. Sharp force trauma3. Projectile trauma4. Miscellaneous trauma
How is a positive identification proved?
Comparison of antimortem records with postmortem findings.
What anti-mortem records can be used for comparison?
- Dental records2. Medical records3. DNA analysis
What should a case report include?
- Background of the case2. Search & recovery3. Details about anthropological analysis including all techniques used4. Summary of findings.
What complementary methods are there to compare a positive identification?
- Photographic superimposition2. Facial approximation
Why must a case report be clear and understandable?
- It is a legal document2. It may be used by investigators and attorneys and become part of court proceedings.3. Must be understood by jury4. Author may be called as expert witness.
What is a Clandestine grave?
Not a ritual burial, concealing the body from police
What are the steps for searching a scene
- Collect information2. Prioritise3. Choose search strategy4. Survey5. Detect anomalies6. Excavate
What sources of information are available to investigators?
- Witnesses2. Confessions3. Intelligence
What is the only evidence that proves the presence of a clandestine grave?
The forensic archaeological excavation
When doing a line search, how dispersed should people be?
2-2.5m apart
What various strategies for searching are there?
Going up/down hill, spiral, corridor, criss-cross
Why the specific distance between searchers?
the peripheral vision is most detailed and overlaps with adjacent searchers line of view
What do you look for during a search?
Changes in soil and vegetation
Why might changes in vegetation and soil be evident?
Decomposing flesh fertilizes soil improving vegetation growth
How is evidence found and marked at the scene?
It is pointed to by a searcher and recorded by the evidence collector. it is then marked with a flag
What are the best conditions in which to perform a search?
- Oblique light (sunrise/sunset)2. Artificial lighting at night3. After rain or snow
What other potential indicators are there for suspicious activity?
Abnormal entomological activity and traces of passage
What supporting tools are used when surveying?
- Metal detectors2. Aerial photography3. Soil restivity4. magnetometer5. Ground penetrating radar6. Cadaver dogs7. Probes8. Stripping
What is the importance of stratigraphic excavation?
- A professional, proactive approach2. Accurate collection of remains and evidence3. Contextual data registration4. Reconstruction of sequence of events
What is the similarity between archaeology and CSI?
Arch: Reconstruction of past events and analysis of physical evidence.CSI: Reconstruction of past events and analysis of physical evidence.
What is stratigraphy?
The analysis of the sequence of deposits in the soil that have formed through natural or human activities.
What is the definition of archaeology?
The documentation by research on the field and by the excavation of the soil. Complete reconstruction of time period & place by the elements.
Define strata
A portion of soil different from the others by shape, colour, composition and hardness.
What is the difference between erosion and destruction?
Erosion - soil moves and accumulates elsewhereDestruction- soil is removed and deposited in a pile elsewhere
What is a stratigraphic unit?
The tangible evidence on the soil left by unique human or natural action.
What is a negative stratigraphic unit?
ONLY A SURFACE. Without volume and content, it is the evidence of destruction (excavation of a grave)
What is relative SU?
The relation between stratigraphic correlations.
What is absolute SU?
Dating according to the elements (artefacts) within.
What should be done if human remains lie on the surface?
- Photograph the scene2. Reconstruct the area of interest.3. Use gridding and mapping to establish spatial control.4. Expose remains with minimal excavation5. Identify the SU6. Collect the exposed remains7. Dig under and near remains8. Sift removed soil
What does the Harris matrix show?
The relative chronology between strata.
What should be done when remains are buried?
- Establish spatial controls2. Remove vegetation and clean area3. Determine area of interest4. Start excavation and determine SU
What should occur during an excavation?
- Take altitude of SU2. Map and take pictures of each SU3. Sift removed soil4. Take soil sample from each SU
Why should a border be left around excavation site? [PICTURE]
In case tool marks are present from offenders digging.
What type of sifting should be used in forensic excavations?
Dry
If there is vegetation growing underneath the corpse, what does this indicate?
Premeditated murder (the grave was open before the body was added).
How should evidence be documented at the scene?
- Progressive ID for each piece of evidence.2. Tag each piece of evidence3. Photograph and map each item before collection.4. Collect each item seperately.
In what direction should documentation of a scene go?
Less invasive to more invasive.Less fragile to more fragile.
What should be done once a piece of evidence has been collected and packaged?
Check the scene again to see if other evidence has come to light.
What type of evidence is placed in large, paper KRAFT bags?
clothes/shoes that need to be dried.
What is a breathable evidence bag?
It allows moisture to escape the bag, but does not allow it to get in.
What type of evidence can be packaged in glass/plastic jars?
Bullets.
What type of containers should guns/knives be packaged in?
Paper boxes/plastic tubes
If tamper-proof tape is not available, how can you ensure it is clear to see if a package has been opened?
Write signature across coloured tape that seals bag.
What is the foam at the bottom of plastic tubes for?
It preserves the blade and prevents compromisation of the container.
When an evidence bag is opened, how should the evidence be re-packaged?
It should be placed in a new evidence bag with the previous bag.
How should an evidence bag be opened?
It should be cut open at the bottom.
What is the benefit of plastic tweezers?
They don’t damage the evidence, metal ones can scratch.
How are fragmented remains reconstructed?
- Acetate sheet placed over the remains2. Pieces drawn on acetate like a jigsaw
What are sterile swabs with tip protectors used for?
Usually DNA samples
What are sterile omni-swabs used for?
Mouth swab
What are self-contained hydration fluid swabs used for?
Dust/pollen collection.
What biohazard risks may be at crime scenes?
- HIV2. HAV, HBV, HCV3. Tetanus
How should excess plaster be removed from a cast?
With hands and water - DO NOT BRUSH (scratching)
What are procedures should the CSO follow?
- No exposed wounds2. Number of CSOs kept to a minimum 3. PPE must be worn4. Not eat/drink/smoke at the scene
What physical risks may crime scenes pose?
- Projectiles (stones etc.)2. Falling3. Electrocution4. Crushing5. Burial6. Respiratory irritation7. Poisoning8. Intoxication9. Explosion10. Fire11. Sunstroke12. Eye irritation13. Acoustic pollution
What does CSO stand for?
Crime scene operator
What does PPE comprise of?
Body: cotton overalls, disposable tyvec suit, PVC apron (lab)Feet: safety footwear, polypropylene overshoesArms: Multiple pairs of glovesRespiratory: Disposable filter with multi-layer seals. (Last thing removed)Head: Goggles, helmetTape: to ensure you are fully sealed with no exposed skin.
What must happen after an investgation?
Authorised personnel must decontaminate the scene.
How is contamination avoided?
- PPE2. Infectious waste disposed of at specific sites.3. Sanitise non-disposable tools
What are the different types of evidence?
- Testimonial2. Documentary 3. Demonstrative4. Physical (pattern & trace)
What are some examples of pattern evidence?
- Fingerprints2. Footprints3. Tyre tracks4. Striation marks5. Handwriting6. Bloodstain7. Powder/pellets8. Char/soot
What is trace evidence?
“Minute bits of physical evidence that may be exchanged among the perpetrator of a crime, the victim and the crime scene.”
Define biological traces.
“Any liquid or solid substance coming from the human body, or which after being in contact with it contains cell remains.”
Give some examples of biological traces
- Blood2. Semen3. Saliva4. Urine5. Hair6. Teeth7. Bone8. Cells/tissues9. Amniotic fluid
On what objects may such traces be found?
- Condoms2. Chewing gum3. Envelopes/stamps4. Paper5. Clothes
What is a reference/standard sample?
Evidence whose origin is known and can be compared to evidence of unknown origin.
What are the stages of investigation of biological traces?
- Sample collection at crime scene2. Packaging, labelling and sending to lab4. Analysis at lab5. Reporting at courtroom.
What are the main components of blood?
- Red cells (erythrocytes)2. White cells (leukocytes)3. Platelets
What is the most common biological evidence?
Blood
Which blood cells contain DNA?
ONLY white
How do we collect reference blood samples?
- Venous puncture - 5ml tube with anticoagulant2. Finger puncture - 3-4 drops. Air dry before packaging.
What is the DNA content of Blood?
30-60 micrograms per microlitre (high)
How do we collect blood traces?
- High amount - Plastic pipette. tube with anticoagulant.2. Small amount - Sterile swab3. Coagulated - plastic spoon
How do we collect traces of blood from objects?
- Small objects - Pack and send to lab2. Big objects: Non-absorbant - Rub with wet swab, scrape off with scalpel.Absorbant - Cut out the stain
What is semen comprised of?
- Spermatozoids (cells) 2. Seminal plasma
What does normal ejaculation contain?
2-6ml of sperm and 100s of millions of cells/ml
How much DNA per sperm cell?
480 micgrams/ml
Is sperm haploid or diploid?
Haploid
How much DNA does saliva contain?
It doesn’t - it is surrounded by epithelial cells which do, bringing DNA content up to 1-10 micrograms/ml (low)
How do we collect reference saliva samples?
- Cheek with a sterile swab2. Taken at least one hour after eating as bacteria degrades DNA3. Left to air dry before packaging.
How much saliva do humans secrete per day?
1-1.5 L
How do we collect saliva traces from objects?
Small objects: Pack and send to labBig objects: Rub with wet swab
What are the components of a tooth?
- Enamel2. Dentin3. Cement4. Dental pulp
What cells make up a tooth?
- Odontoblasts (dentin)2. Cementoblasts (cement)3. Ameloblasts (enamel)4. Osteoblasts (alveolar bone)5. Fibroblasts (Periodontal ligament)
Where does most DNA from a tooth come from?
Dental pulp (blood vessels)
Where are the majority of nucleated cells found in the tooth?
Dental pulp
How else can we obtain DNA from teeth in children?
Dental germs (Less DNA and poorer quality than adults)
What is bone tissue made up of?
- Intercellular matrix (hydroxapatite and collagen)2. Bone cells (osteocytes and osteoblasts)
What are osteocytes and osteoblasts?
Nucleated cells
How many osteocytes/osteoblasts do we find in compact bone?
20000-26000/mm3
What is the DNA content of bone?
3-10ng/mg (very low)
The spleen contains a high amount of nucleated cells, so what is the problem with collecting DNA from here?
It is the first organ to degrade after death, very quickly.
Which bone is most successful for obtaining DNA?
Sternum
Do nails contain DNA?
No - epithelial cells swept along during growth.
What do nails contain?
Keratin (Fibroprotein)
What protein is hair made of?
Keratin
What does the hair shaft contain (cut)?
Mitochondria
When do we collect hair reference samples?
Only when blood/swab sampling is not possible.
What does the hair bulb contain (pulled)?
Nucleated cells
How many hair reference samples do we collect?
10-15 samples with roots.
How do we collect hair traces?
- Sterile forceps2. Package separately3. Use sealing paper bags
What is the meaning of Desquamation?
To shed an outermost layer/membrane
What 6 types of Desquamation cells are there?
Simple/stratified - Squaremous, cuboidal or columnar
Are all Desquamation cells eukaryotic?
Yes
What are the 4 main problems when collecting DNA samples at the crime scene?
- Contamination with biological material2. Transference of biological traces3. Sample degradation 4. Chemical/physical treatments
What is the role of PPE?
To avoid contamination and lower the risk of infection when collecting biological evidence
Why must any biological samples contains DNA be kept in a refrigerator?
The DNA degrades in hot conditions
What is the first type of evidence to be collected?
Biological as it will degrade