Fundamental Forensic Techniques Flashcards
Define chain of evidence/custody
An evidence record of all the individuals who have had physical possession of the evidence for whatever reason
When should evidential reports be made?
At the time or as soon after the event as possible
Define hearsay
Information gathered by one person from another concerning something of which the second person had no direct experience
What are the four essential conditions which must be fulfilled before an S9 statement is admitted as evidence in court?
- The statement must be signed in all appropriate places by the person making it
- It must be endorsed with the S9 declaration which must also be signed
- A certified copy of the statement must be served on the opposition and court prior to the hearing
- The content of the statement must be agreed and not subject to any form of dispute
Where should the person writing the S9 statement sign?
Under the declaration
At the bottom of each page
After the last word of the text
All mistakes and corrections initialled
Any alterations or additions initialled
What does ELBOWS stand for?
Erasures
Leaves torn out
Blank spaces
Overwriting
Writing between the lines
Strike through
What are the factors of the order in which you recover evidence governed by?
Evidence decay rate
Ability to recover
Relevance to scene
Likely weight in court
What are the 5 elements to a final sketch?
Heading
Diagram area
Legend
Title block
Scale and directional notes
Why should a sketch have a heading?
States why the sketch was created
Why should a sketch have a diagram area?
It includes the drawing itself. It needs to be a balance between information included vs amount of clutter
Why should a sketch have a legend?
Short hand will need to be used and the legend allows the text to be shifted out of the sketch itself in to another area
Why should a sketch have a title block?
Provides key information to the person observing the text
What should a title block include?
- The report number, or CJ art exhibit ref
- Physical address of the scene
- Name and rank of sketch creator
- Time and date the sketch was created
Why should a sketch have scale and directional notes as compass directions?
In order to help with evidence, such as finger marks
What should be disclosed?
- Unused materials (materials on which the Crown do not reply)
- Material which may tend to support the defence or undermine the prosecution
What are the 4 ways a sketch can be drawn?
Birds eye view
Exploded view
Elevation sketch
Three-dimensional sketch
What is the most accurate way of determining where an object is on a sketch?
Triangulation
What is the major and minor component of fingerprint impressions?
Major - water
Minor - amino acids
The mark hidden or invisible requiring enhancement to visualise it is said to be..?
Potent
A fingermark left on a soft material, such as put or wax, is referred to as which type of fingermark?
Plastic
What surface are fingerprint powders most useful for developing fingermarks?
Porous
Define latent fingermarks
Those which are hidden or invisible. They usually come from a transfer of body perspiration or oils and must be enhanced
Define patent fingermarks
Ridges placed on a surface after contact with a coloured material, such as blood, paint, grease, and ink
Define plastic fingermarks
Ridges left on a soft material, such as putty, wax, soap and dust
Define porous surface
Any surface that rapidly absorbs the latent fingerprint deposit
What are physical developers designed for?
To react with one or more components present in the deposits of the fingermark without damaging the deposited material
What factors effect the retention of the deposit on a surface? And why?
The temperature of the surface - sebaceous deposits will adhere to a surface below bodily temperature
Surface structure - tougher = better adhesive effect
Forces - electrostatic forces on the substrate –> a similar charge will repel absorption of some ions and an opposite charge will favour it
How do time and environmental conditions effect fingermarks on porous surfaces?
- Amino acids tend to remain stable as long as the substrate is stored below 80% relative humidity
- Other compounds such as urea and sodium chloride will tend to migrate dependent upon the environmental conditions (humidity most important)
- The higher the humidity the faster the migration
Define non-porous surface
A surface that does not absorb any component of the latent fingerprint deposits, such as glass, mirror, plastic, and painted surfaces
Define semi-porous surface
Any surface that does not fit well into the porous or non-porous groups, such as polymer banknotes, waxed wrapping paper, some fabrics, and some paper/card combinations
Define developers
Chemicals, powders, and processes which develop into a latent print
What are the three categories of developers?
Physical, chemical, and special illumination
Give examples of metallic, non-magnetic powders for lifting fingermarks
- Aluminium oxide
- Titanium oxide
- Gold
Give examples of non-metallic powders for lifting fingermarks
- Carbon
- Kaolin
- Treated starches
- Talcum
What powder should you use for patterned surfaces?
Fluorscent
What is the metallic magnetic brush used for?
Damp surfaces and surfaces such as paper
How do metallic magnetic brushes work?
Grains are coated with steric acid which has an affinity for amino acids and lipids, therefore adhering to NWS residues
What is small particle reagent (SPR) and how does it work?
A suspension of fine molybdenum disulphide particles in detergent solution. It adheres to fatty acid constituents of latent prints, allowing for the development of fingerprints on wet surfaces
What type of surface is SPR used on?
Non-porous only
What happens if SPR is used on a porous surface?
The water/detergent solution will be absorbed and the MoS2 will be prevented from settling on the NWS residue
What does CEF stand for?
Cyanoacrylate Ester Fuming
Describe the CEF method?
- The cyanoacrylate must be in gaseous form
- A few drops of super glue are placed into an open container directly above a heat source
- A concentration of gaseous cyanoacrylate forms once the b.p (49-65C) is reached
- Moisture aids the reaction, so a beaker of hot water is placed into the cabinet
- If any latent prints are inside the tank, they will be exposed to the gaseous cyanoacrylate
- Fumes from the glue adhere to the print, producing a visible, white print
Describe the CEF mechanism
- Super glue reacts with traces of amino acids, fatty acids, and proteins in the NWS residue and moisture in the air
- This causes the deposition of a hard white precipitate on the NWS residue
- A robust fingerprint is developed
What are the problems with CEF?
- Difficult to set up
- Actual experiment can take up to two hours (depending on cabinet size, cyanoacrylate concentration, and humidity)
- Not possible to calculate time needed to perform the experiment
- Reaction must be monitored as prints can get overlapped
- Chemical deposition will continue until the ridge images overlap
- Fumes are an irritant
How does ninhydrin work?
It reacts with the amino acids deposited in the perspiration from the sweat glands of the fingers. It forms Ruhemann purple which makes the fingermark visible
What are the advantages of vacuum metal deposition?
- Extreme sensitivity
- Can reveal old prints and prints exposed to water
- Can detect monolayers of fat on smooth surfaces
- Can sometimes reveal fingerprint detail when all other techniques have failed
What are the disadvantages of vacuum metal deposition?
- Initial cost of equipment
- Zinc will eventually oxidise, so photos must be taken immediately
How does VMD work?
- Evidence is placed in a vacuum chamber
- The chamber is brought to a vacuum and a few milligrams of gold is evaporated to form a very thin layer of metal on the surface
- The gold film is uniformly distributed across the surface of the evidence penetrates the fingerprint deposit
- Zinc is added to the chamber
- The zinc binds to the gold but does not penetrate the fingerprint deposit
- The ridges appear transparent, whereas the furrows and the background are dark
What surfaces is VMD best used on?
- Smooth, non-porous surfaces
- Plastic packaging materials
- Smooth leather surfaces
- Photographic negatives and prints
- Plastic mouldings
- Glass
- Smooth paper
- Some smooth fabrics
What is physical developer?
A silver nitrate-based reagent which is used when other chemical methods are ineffective. Latent fingerprint on paper initiates deposition of silver
How does silver nitrate help develop fingermarks?
A silver nitrate solution will develop latent prints by reacting with sodium chloride found in the sweat residue. When exposed to light a black outline will form on the ridges. When the silver chloride reacts with light, the chloride is converted to chlorine gas, leaving free silver
How is iodine used to develop fingermarks?
Iodine vapour is absorbed by the oily residues deposited in fingerprints
Define sequential processing
Different types of surfaces require different treatment sequences. Use of one process after another can double the number of developed fingerprints
What are some examples of demonstrative evidence?
Charts, videos, recordings, photographs
What are examples of documentary evidence?
Documents, wills, letters, confessions, suicide notes
What is exculpatory evidence?
Favourable to the defendent
What is inculpatory evidence?
Evidence which tends to increase the likelihood of fault or guilt
Define physical evidence
An object or item that establishes that a crime has been committed and link a crime to its victim or perpetrator
Give some examples of physical evidence
Blood, semen, documents, fingerprints, explosives, hair, impressions, DNA, serial numbers
Define trace evidence
Physical evidence that is found in small but measurable amounts, such as strands of hair and skin cells
Define transient evidence
Temporary evidence which is easily changed or lost, such as odour, temperature, and fragile evidence
What is conditional evidence?
Evidence produced by a specific event or action which helps to determine the sequence of events, such as bodies can be moved
What is individual evidence?
Evidence attributed to a common source with a high degree of certainty, such as DNA evidence or fingerprints
What is class evidence?
Evidence associated with a group and never a single source, such as shoes and unused bullets
What is associative evidence?
Evidence which associates a victim or suspect with a scene or each other, such as personal belongings
What is biological evidence?
Evidence which has originated from a human, plant, or animal, such as bodily fluids
What is circumstantial/indirect evidence?
Evidence which provides a basis for interference about a disputed fact
What is pattern evidence?
Evidence produced by direct contact between a person and an object, or between two objects, such as blood splatter, indentations, and tire marks
What is transfer evidence?
Evidence produced by contact between person(s) and object(s), or between person(s) and person(s), such as fibres, hairs, and paint
What is the job of the investigator and forensic expert at the scene of an incident?
- Work together to define and secure the crime scene
- Examine and document the scene
- Collect physical evidence, preserve it, and package it
- Submit the evidence to other agencies
What does EDSA stand for?
Electrostatic document analyser
Why must ESDA have a vacuum stage?
So that the item can be drawn flat on the surface and a polyester film placed on top of it
What is the purpose of a corona wand?
To be passed over the surface of the polyester film to develop an electrostatic charge pattern on it
Why must an ESDA machine have a tilting bed?
So the toner powder can be cascaded across the surface of the charged polyester film
Define capacitance
The ratio of the change in electric charge of a system to the corresponding change in its electric potential
Why should ESDA be used before fingerprint techniques?
ESDA is non-destructive
What is historical dating?
Verification of the age and value of the document
How does ESDA work?
It uses electricity in the corona wand to induce a charge distribution. Intended areas of the document carry less negative charge than surrounding areas
What is fraud investigation?
Focuses on the money trail and criminal intent
Define a questioned document
Any object that contains handwritten or typewritten markings whose source or authenticity is in doubt
Define simulated forgery
One made by copying a genuine signature
Define traced forgery
One made from tracing a genuine signature
Define blind forgery
One made without a model of the signature
What are the rules when collecting handwriting exemplars?
- The writer should be sat comfortably without distraction
- The suspect should not be shown the questioned document
- The suspect should not be given any help or instructions with grammar
- The suspect should be given similar pen and paper to the questioned document
- The dictated text should be very similar, if not the same, as the questioned document
- Dictation of the text should take place at least three times
What does VSC stand for?
Video spectral comparator
What is the use of a VSC?
To analyse documents and links
What is infrared luminescence?
Many inks, when they are irradiated with blue, green light will absorb the blue and give off radiation in the infrared spectrum
What are the two techniques used to convert a near infrared image to a visible image?
- The document is illuminated with near infrared illumination and its image is examined through a series of optical filters
- The document is illuminated with intense visible light that has been filtered to be nearly free of infrared radiation, and so fluoresces. Any difference in fluorescence will become evident
What are the common ways of altering a document by erasing parts of it?
- Eraser
- Sandpaper
- Razor blade
- Knife
- Chemicals
What does ESLA stand for?
Electrostatic lifting apparatus
What is the job of ESLA?
To make shoemark impressions visible
What is a 2D footwear impression?
An impression made when the undersole of a shoe encounters a hard, flat surface
What are positive and negative impressions?
Positive - transfer of material from the sole to the surface
Negative - removal of residue from a flat surface
What surfaces can ESLA be used on?
Any which are dry
What are two problems with ESLA?
- Shoes will wear differently for each wearer due to the characteristic walk patterns of individuals
- Each time someone takes a step the shoe will wear further
How do you take comparison show marks?
The examiner wears he show and the soles are covered in a water-based ink using an ink pad. The shoe is then carefully stepped onto the tracing paper or an acetate sheet
Give a short explanation of how ESLA works
- A sheet of mylar film is placed on top of a dust mark
- A high voltage is applied across the surface of the film. This causes a charge difference between the film and the surface below
- This causes the dust prints to be adhered to the surface of the film
Define surface tension
cohesive forces between liquid molecules causing the attraction of particles in the surface layer by the bulk liquid
Define specific gravity
Force placed upon a substance, associated with weight
What happens to size of the circular pattern of blood as the distance between the source and the surface increases?
The size of the circular pattern increases, but only until 122cm after which it remains consistent
When should post mortem wounding distribution calculations be considered?
If there is anomalous impact or distribution data
What is the effect of blood viscosity on BPA?
The higher the blood viscosity, the less spread there is on impact
Define angle of impact
Angle at which a drop strikes a surface
Define parent droplet
The main droplet under examination
Define satellite droplet
Smaller droplet originating from the parent droplet
What are spines in terms of BPA?
Lines of blood radiating from the parent droplet
What are the three categories of blood stains? Can you give some examples of each?
- Passive - clots, drops, flows, and pooling
- Transfer - wipes, swipes, pattern transfers, and contact stains
- Projected or impact - spatters, splashes, cast-off, arterial spurts, and expirated stains
How are passive bloodstains formed?
From the force of gravity
What are transfer bloodstains?
Bloodstains which are deposited on surfaces as a result of direct contact with an object which has wet blood on it
What is a drop bloodstain?
A pattern of blood created when a volume of blood strikes a surface at low to medium velocity. These are low volume and low velocity impacts
What are pool bloodstains?
A pattern created when blood collects on or flows on to a surface at low velocity with large volumes
How do you know if a pool of blood has been present for a while?
The middle of the pool will be darker as red blood cells retract to the centre and plasma moves toward the outside of the pool
What is a spray bloodstain?
A bloodstain created by blood that is expelled from the mouth or nose due to an internal injury
Why are spray bloodstains usually lighter in colour than other stains?
They have been diluted by saliva
What are smear bloodstains?
A bloodstain formed by the transfer of blood from one surface to another, or when an object is dragged through an existing pattern
What is a spurt bloodstain?
A pattern created when a victim suffers an injury to a main artery or to the heart
What makes spurt patterns distinctive?
The spurting of the blood is in time with the beating of the heart and so large looped arch patterns are created
What is a cast-off bloodstain?
Blood which has been thrown from an object
Why are cast-off stains useful?
Bloodstain tails will point in the direction that the object was moving, ad the width may help to suggest which type of object produced the pattern
Define skeletonisation
When the edges of a stain dry to the surface
How long does it take for skeletonisation to occur?
Usually within 50 seconds of deposition for drops, but longer for larger volumes of blood
Define point of origin
The point where the blood was released
What factors can affect the calculations for the point of origin?
- Multiple velocities
- A strong crosswind
- A deliberate misdirection
What is the equation for the angle of imapct?
sin(A) = width of blood stain/length of blood stain
Define base group
Any distribution where the droplets form perfectly circular droplets
What are the factors affecting the reliability of BPA?
- Motion of the point of origin
- Multiple droplet velocities
- Overlaid pattern
- Impact surface texture
- Deliberate misdirection
- Strong crosswind
- Multiple wounds/impacts
- State of the victim
What is one of the first things you must do when dealing with blood?
A presumptive test to identify if the material is blood
How is luminol used to detect blood?
It is sprayed on to the suspected area and when it reacts, light is produced which is enhanced using an alternative light source.
What is the main drawback of luminol?
It produces many false positive as it reacts with lots of different substances
What are the three different categories of homicide offence?
A - a major crime of grave public concern, such as multiple murders
B - routine major crime where the offender is not known
C - a major crime where the identity of the offender is known
What are the five building block principles upon entering a scene?
- Preserve life
- Preserve scene(s)
- Secure evidence
- Identify victim
- Identify suspects
When there are two scenes at one crime, what is the main way they become contaminated?
Staff moving from one scene to another
What do you need to consider when thinking about why a crime has happened to a particular person?
Routine
Risk
Lifestyle
Associates
Links to the scene
Physical appearance
How controlled
Personality
Precursor incidents
Relationships
Define offender assessment
The consideration of the offender’s method of operation (MO)
What is the purpose of a method of operation?
To ensure the success of the venture, protect the identity of the offender, and ensure the escape and prevent subsequent identification
What are the main motives to consider?
Gain
Jealousy
Revenge
Elimination
Conviction
Lust
Thrill
Hate
What is the number of fibres that are transferred between items dependent upon?
The nature of the donor fabric
The nature of the receiving fabric
The degree of contact
What is the order of actions when collecting clothing evidence from a sexual offence?
- The subject should be asked to stand on a sterile mat
- Asked to remove one item of clothing at a time
- The item of clothing should be placed on the mat
- The subject should then stand on a second mat
- The first mat should be wrapped around the item
- The whole sample should be bagged in paper sacks
What is the process for collecting hair after a sexual offence has occurred?
Hair should be combed onto sterile paper using a new comb for each area of the body as they are all separate samples
What is the process for collecting evidence off of nails in crimes where a sexual offence has occurred?
Each nail should be scraped over a sterile mat or into a polythene bag, the mat is then wrapped around the scraper and placed in the refrigerator
What is the presumptive test for detecting semen?
Acid phosphate test
What is the result if the AP test for detecting semen is positive?
A rapid colour change to purple within 30 seconds
What is the confirmatory test for semen?
Looking under a microscope
List some of the multiple reasons for no sperm heads to be found
- Aspermic
- Oligospermic
- Use of spermicide
- Use of contraceptives
- No ejaculation to area examined
- Incident did not occur as alleged
What is the test for saliva and how does it work?
Phadebas test
Amylase breaks down the starch in the saliva and releases the blue dye, hence a blue colour develops within 5 minutes
What can cause false positives on the Phadebas test?
Faecal material, vaginal secretions, sweat, and urine
Define a scene
Any location from which evidential material may be recovered
What are the three levels of the Unified Command Structure?
Gold (strategic)
Silver (tactical)
Bronze (operational)
What is a Forward Control Point (FCP)?
A fixed location that is identifiable and accessible
What does METHANE stand for when referring to major scenes?
Major incident declared?
Exact location
Type of incident
Hazards present
Access
Number
Emergency services
Define outer cordon
This is marked by blue tape and used as the holding area for resources and personnel and is the buffer between the sterile scene and the public
Define inner cordon
This is marked with red tape and is the area from which evidential samples will be recovered
What is a common approach path (CAP)?
A single access point that is used for entry and exit of the scene by everyone
