Ch. 9- Basic Skills For Scene Processing
Methodology employed in bloodstain pattern analysis...The technician:
* Becomes familiar with the entire scene * Identifies the discrete patterns among the various bloodstained surfaces * Categorizes these patterns based on the established taxonomy of bloodstain pattern analysis * Evaluates aspects of directionality and motion in the stain or pattern * Evaluates interrelationships among stains, patterns, and other evidence * Evaluates angles of impact, points of convergence, and areas of origin (if necessary) * Evaluates viable source events to explain the pattern (based on all of the above)
methodolodgy for crime scene investigation from O'Hara:
*Painstaking, comprehensive collection of data *Arrangement and correlation of that data *Definition of issues and investigative questions *Development of a hypothesis along the lines of the available data and subsequent resolution of any hypotheses 8testing of the hypothesis and elimination, when possible, of contradicting hypotheses *Testing of final hypothesis before acceptance
On scene examination of latent blood prints:
1. Amindo-black 2. leuco-crystal violet 3. fluorescein (alcohol-based not aqueous) *Never use luminol or aqueous based fluorescein in an attempt to develop latent prints *Wet surface-dry surface then apply techniques above
Three basic on scene fingerprinting techniques:
1. Basic powder techniques (standard and magnetic) 2. Superglue fuming 3. Small particle reagent *Also be experienced in recovering prints from human skin using the adding machine paper technique and in the use of crystal violet solutions on adhesive tape. Also the recongize methods of recovering latent prints at fire scenes
the most common fire signs found in the fire scene?
1. Char patterns 2. smoke and soot patterns 3. Damage patterns
Steps in Event Analysis
1. Collect Data, Establish Likely events 2. Establish Event segments from the data available 3. Define Associated Event Segments 4. Order and Sequence the Associated Event Segments 5. Audit the Information 6. Determine and Final Order the Events 7. Flow Chart the Overall Incident Based on the Event and Event-Segment Sequence
On scene examination of adhesive surface:
1. Crystal violet, alcohol/water technique 2. Sticky side powders (wet surface allow to dry before trying any of the above-techniques)
On Scene examination of rough non porous surfaces:
1. Cyanoacrylate fuming 2. Powders (consider fluorescent for contrast)
On scene examination order for paper:
1. DFO 2. Ninhydrin 3. Silver Nitrate
Ballistics is broken down into three areas of study:
1. Internal or interior ballistics 2. terminal ballistics 3. External or exterior ballistics
Fingerprints can exist in 3 basic forms:
1. Latent Print 2. Patent Print 3. Plastic Print
To determine angle of impact:
1. Measure the long and short axis of the stain without the tail or scalloping 2. Divide the short axis by the long axis (should be less than 1) 3. Determine the inverse SIN of this number
On scene examination of untreated wood:
1. Ninhydrin 2. Powder/brush
Other than wet surfaces, SPR can be effective in what other situations?
1. Oily windows 2. Oxidized metals 3. Galvanized surfaces 4. Salt water sprayed areas
Two issies with the brush and powder techniques:
1. Overpowder a latent print 2. Applying too much pressure when dusting the print
Bloodstain patterns are grouped into two basic categories:
1. Passive stains 2. Dynamic patterns
Two primary field test for the presumptive presence of blood
1. Phenolphthalein 2. Leucomalachite green
Areas of specific consideration when searching for fingerprints...
1. Points of entry 2. Points of exit 3. Any appropriate surfaces in and around the area where the actual crime was committed
On scene examination of glossy surface paper:
1. Powder/brush 2. Cyanoacrylate
When a smooth non porous surface is wet:
1. Seize and dry followed by the usual techniques OR 2. Small particle reagent
When a porous surface is wet:
1. Seize and dry-follow by physical developer
Other processes that may work on non porous smooth surfaces:
1. Silver nitrate may work on some plastics 2. Iodine fuming may be effective on fresh prints other than those located on metal
On scene examination of human skin (alive):
1. adding machine paper technique
On scene examination of human skin (dead):
1. adding machine paper technique 2. cyanoacrylate fuming 3. magnetic powder 4. iodine fuming
On scene examination of all non porous smooth surfaces:
1. cyanoacrylate fuming 2. powders (consider fluorescent for contrast) 3. Small particle reagent
Fire requires what to exsist?
1. heat 2. fuel 3. oxygen 4. uninhibited chemical chain reaction between the three *Known as the fire tetrahedron
The disipline of bloodstain pattern analysis considers...
1. location 2. shape 3. size 4. distribution 5. other physical characteristics of bloodstains
Primary methods for enhancing latent or slightly visible bloodstains
1. luminol 2. fluorescein 3. amido-black 4. leuco-crystal violet (LCV)
On scene examination of visible bloody prints:
1. photograph and lift or enhance with powder 2. Amido-black 3. Leuco-crystal violet
Scene conditions at fire scenes...
1. the fire damage itself 2. the resulting creation of unstable structures, 3. the presence of significant debris covering evidence 4. the fact that burned surfaces are black and do not reflect light effectively
Phenolphthalein consists of what three basic solutions
1. the phenolphthalein solution itself 2. ethanol 3. hydrogen peroxide as an oxidizer
Stock solution of crystal violet:
1.5 grams of crystal violet powder in 100 ml of ethyl alcohol.
Long elliptical bloodstains indicate an impact angle of
10-30 degrees
When luminol is prepared from bulk the mixture is
100ml of distilled water, 0.1g of luminol, 0.7g of sodium perborate, and 0.5g of sodium carbonate
At what temperature does flash over occur?
1100 degrees F
Heat energy and thermal imaging wavelength?
12,000nm
Shortwave UV wavelength
180-254nm
Fill dirt is removed from gravesites in what size layers?
2 inch layers across the entire surface until a stratum or artifact is located.
Working solution of crystal violet
2ml of stock solution per 100 ml of water
Longwave UV wavelength
365-415nm
Crime scene search filters employ a broad passband filter encompassing _ nm?
390-520nm
Visible light spectrum in nanometers
400nm (violet)-700nm (red)
Near UV and Violet wavelength
415nm-485nm
Blue light wavelength
485nm-530nm
Orange-Red wavelength
570nm-700nm
Infrared wavelength
700nm-2000nm
Lifting of prints on rough non porous surface:
After powdering use a silicone based casting material, textured surface lifting tape, or textured surface lifting material
Barrier Filter
Barrier filter keeps the orginal wavelength from passing, but allows fluorescence energy to pass and be seen
At 455nm?
Biological fluids are easily observed in combination with an orange barrier filter
Name of latent processing technique that provided the idea to process fire scenes with a more critical eye...
Camphor technique.
Taxonomy of stains
Classification of stains
Most import tool the Crim Scene Technician uses in any crime scene?
Clean white light
Excitation Filter
Creates specific wavelength
Reflected light
Defines the color of the object we visulize. The object absorbs all colors except the one we visulize, ie blood absorbs all colors except for red.
A clandestine gravesite may exhibit what appearances?
Disturbed soil, a grave mound, or even soil compaction. Vegetation around the immediate grave is likely to have been disturbed by the activity therefore it may be absent or in a state of regrowth that is dissimilar to the surrounding vegetation.
How do u test for copper in a defect?
Dithio oximide. 10% ammonia on the filter paper applied to the defect. Then spray with DTO. Positive test then it will turn green
On scene examination of wet rought non porous surfaces:
Dry, followed by powder and brush technique
ESLD
Electrostatic lifting devices
Fire patters do what?
Fire patterns show the progress of the fire, demonstrate the nature of the fuels involved and help to locate and isolate the actual origin of the fire. Visible and meaurable physical effects on the material in the scene.
At 485nm?
Latent prints developed in ninhydrin and be visualized using a yellow barrier filter
UVA
Longwavve UV
Fluorescence
Luminescence that happens as long as the object is exposed to an active energy source (ie ALS)
What types of nonintrusive technologies can be used to help locate a gravesite?
Magnetometers, ground penetrating radar, and infrared thermography; also a trained cadaver dog
SPR consists of...
Molybdenum disulfide suspended in water solution.
Muzzle ranges: Close contact or hard contact
Muzzle is in direct contact with the skin or pressed into the skin
ESLD works on what concept?
Opposites attract
What method drives every fire investigation?
Origin and cause
When using orange-red wavelengths us what barrier filter?
Red barrier filter
RUVIS
Reflected ultraviolet imaging system
450nm is good for?
Searching for/visualizing bite marks/bruises on human skin when used with a yellow barrier filter
UVB/C
Short wave UV
Define SPR
Small particle reagent
What can blood spatter analysis provide the investigator?
Specific information relating to where the associated event occured, what items were involved in the event, and the relative position of people and objects at the time of the event.
What happens to blood stains when exposed to longwave UV?
The bloodstain absorbs all the light of that bandwidth, reflecting nothing back, thus will appear black
What four basic ways can light energy act on an object?
The energy will be reflected, absorbed, transmitted, or converted (or any combination of the four)
Release of energy
The excited electrons fall back to normal energy state, releasing energy as light. This release is at a lower energy state than the original light.
Phosphorescense
The object continues to give off light in the converted wavelength even after removal of the energy source.
What happens to biological stains when exposed to longwave UV?
The will fluoresce with a lime green color even without a barrier filter
False positive reaction differences in luminol
There is a differenct in color, duration, and intensity. Flase positives usually is an immediate and intense reaction (almost a flash of light) that dies out quickly. Color is more light green/white. Toliets can present long duration blue violet color response
How is the presence of metallic lead in a suspected defect evaluated?
Using a sodium rhodizonate test
On scene examination of wet human skin:
Utilize the adding machine paper technique which is not negatively impacted by moisture.
455-485nm can be used to?
Visualize fluorescein reactions with latent blood. Typically using a yellow filter but an orange filter can be effective too when using the higher wavelengths
When should the reaction be halted in superglue fuming?
When the test print first begins to appear.
The color white represents...
a reflection of all wavelengths
The color black is...
an absorbtion of all wavelengths
Drip patterns occur when...
an object dripping blood is stationary for a period of time.
the presumptive tests are based on...
an oxidation-reduction reaction of chemicals that occurs in the presence of heme, a component of hemoglobin
Impact angle
approximate angle at which a droplet struck a surface
Dynamic patterns
are created by foreceful events, where fluid blood is projected out from a source under some force or compression. ie spatter, castoff patterns, arterial patterns, splashes, and spines
Patent Prints
are fingerprints caused by the deposit of contaminants such as bloody or greasy finger marks
Forensic firearms examiners
are the people who deal with internal ballistics. This includes the study and examination of the firearm itself, which includes ejection patterns, gunshot residue deposition, and other related aspects.
Fire patterns
are the predictable behaviors of fire that leave both blatant and subtle effects.
Bear claw shaped bloodstains indicate an impact angle of
between 40 and 60 degrees
circular bloodstains indicate an impact angle of
between 70 and 90 degrees
Rubberized casting compounds are not effected for recovering...
bite marks from human skin or for casting dirt impressions.
Saturation stains occur when...
blood is drawn into clothing, cloth, or pereable items. Often mar or destroy other blood patterns of interest
Contact stains occur when...
blood is transferred from one object to another through some form of contact ie. pattern transfers, wipes, swipes, and saturation stains
Directionality of a bloodstain is defined by
both the long axis of the stain and the presence of scallops, tails, and satellite spatter.
Point of convergence
by visualizing a line aligned with the direction angle and extended back into the scene (reverse vectors) for a number of related spatters, a point of convergence will form where the lines cross each other on a surface
Damage patterns
can be evident on a single object or extended across an entire room. As an object is subjected to flame and heat from the fire, the exposed surfaces are damaged.
Luminol can have false positives from what items
certain metals, vegetable peroxidase, and cleaning cemicals
Terminal ballistics
considered by the forensic pathologist, the effect of projectiles on the body
External ballistics
considers the trajectory of the bullet after leaving the weapon. The information derived is dependent upon the scene and the targets incolved.
"events" in event analysis
define gross aspects of the incident, such as approaching the scene, controlling the victims, killing the victims, etc
Luminol is a combination of
distilled water, luminol, sodium perborate, and sodium carbonate
Flurescein solution is
distilled water, sodium hydroxide, fluorescein, and zinc. 25ml of disilled water with 0.25g of fluorescein and 0.5g of zinc
Alternative light sources (ALSs) allow the crime scene technician to...
employ a variety of narrow wavelengths of the light spectrum in an effort to identify, visualize, and document a variety of different types of physical evidence.
Plastic Prints
fingerprint impressions where a print has been deposited in a soft surface such as wax p.27
Typical pattern transfers include...
hand or foodprints and patterns of bloodied knife blades or blunt force weapons
Rubberized casting compounds are most effective when used on...
hard substrates such as metals, wood, bone, or plastic.
Special condition surfaces:
human skin, adhesive tapes, and blood prints
At 525-530nm?
in combination with an orange barrier filter are excellent for developing and visualizing latent fingerprints with fluorescent powders
Latent Prints
invisible prints created by the deposit of normal body secretions.
Most basic consideration of light
is ensuring the presence of light of sifficient illumination on scene in order to conduct a thorough search.
Absolute chronology
is related to timing aspects.
The "incident" in event analysis
is the overall situation being investigated
Relative chronology
is the seuencing of event segments in relation to one another. Relative chronology is thetrue back bone of the reconstruction. No association with absolute time.
Area of origin
is the three dimensional space above the convergence point
Sodium rhodizonate test consists of what?
it requires 3 working solutions. 10-15% solution of glacial acetic acid. then a working solution of sodium rhodizonate (4g to 100ml of water), which should turn scarlet if lead is present. then 5% hydrochloric acid which should turn the scarlet to blue violet
Transmission of light relates to
its penetrating power;light energy can pass through and object
Conversion of light
light energy can be converted from one wavelength to another, creating the condition known as luminescence.
Thermal imaging has been used effectively to...
locate decomposing bodies and to find hot spots in fire scenes. Also available in a handheld device to distinguish between recent and older tire marks on accident scenes.
"event segments" in event analysis
microcomponents of the event. sevent segments are snapshots of specific moments in time, detailing specific actions that occurred. Event segments are always defined by specific data.
Muzzle ranges: Intermediate range
muzzle is between 5-40 inches. intermediate range gunshot wounds are deduced from the presence of stippling around the wound. Different types of powders travel and embed at different distances, resulting in an ability to define the wound as intermediate
Muzzle ranges: Loose contact
muzzle is in extremely close proximity to the skin but at the moment of firing a gap is created between the two
Muzzle ranges: Near contact
muzzle is not more than 5 inches from the skin
Critical consideration in superglue fuming is...
not to overfume the latent print.
Fly spot
occur as the result of fly activity in a scene. The movement of flies can track blood from a body or blood source and deposit it on surrounding walls and surfaces. Flies also regurgitatae blood onto these surfaces.
Swipe pattern
occur when a bloody object makes contact through some for of lateral motion with an unstain object
Wipe patterns
occur when a prexisting stain is disturbed by another object
Void patterns
occur when a secondary object is present between a bloodstain event and a nearby surface. Voids appear most often in spatter events
Splash patterns
occur when a volume of blood is projected into the scene with minimal force
Cast off patterns
occur when an object is bloodied and then moved or swung with some force.
Porous surface examples:
paper, cardboard, untreated wood
Infrared wavelengths are most often employed in...
questioned document examinations. Has little direct application to crime scene processing.
Passive Stains
result from an action other than a directed force to a blood mass ie. contact patterns, blood clots, drip patterns, drip trails, and blood pools or flows
Arterial patterns
result from blood in volume that is projected into a scene under pressure from an artery or heart
Smoke and soot patterns
result from the outflow of fire products
Directionality of the stain
the direction the droplets were traveling at the moment they struck a surface
Stippling or tattooing is
the embedding of unburned and partially burned gun powder residues in the skin
SPR reacts with what in a latent print?
the fats found in the latent print
All radiant energy is measured by...
the length of its wave (from peak to peak), wavelengths are measured in nanometers
Refractive Index (RI)
the manner in which it allows light to pass through it
Consdieration is also given to...
the nature of the object and how one would typically touch or manipulate the item.
The basis of all crime scene reconstruction is...
the scientific method
Intrusive techniques for locating a grave are...
the use of probes and vapor monitors. Vapor monitors are used to detect decomposition gases
Muzzle ranges: Indeterminate range:
this determination means that no conclusion can be drawn on muzzle distance. This determination is found in situations where there are no markings except for the bullet defect
How is fluorescein reaction seen
using an ALS set between 455-485nm with a yellow barrier filter. orange will also work
Char patterns
usually result from direct flame involvement
Nonporous smooth surfaces:
varnished and painted surfaces, plastic surfaces, glass
Orange and red wavelengths are effective for...
viewing inks on items present in the scene as well as questioned documents. May also assist in visualizing subcutaneous bruising.
Nonporous rough surfaces:
vinyl, leather, textured countertops, and other textured surfaces
Pyrolysis
when heat breaks down the fuel source into gas and vapors that burn
Expiratory spatter
where there is blood present in the airway and exhalation of the victim will break the blood into small droplets, which are forced out of the airway
