Impression Evidence
General & Scene Considerations
OverviewImpression Evidence
Anything that leaves an impression can be compared with an original
Class Characteristics
Marks produced during manufacture AND during routine use– Made during the manufacture of the tool or the object
Accidental or Unique Characteristics Small (or microscopic) unique (accidental) marks are thought to be traceable to
a specific object Occur during normal useage
Classifying Footwear Impressions Three categories:
Visible: Occur after someone steps into a foreign substance and then transfers the substance to a clean surface.
Depending upon the background color, a visible print may be a simple impression made from dust on the sole of the shoe.
Plastic: Occur when someone steps into a malleable (soft) surface and leaves a three-dimensional impression.
Typically, this could be an impression in mud or cement.
Latent: Those that are invisible to the naked eye and typically require an aided eye to make them visible.
2D Impressions Defined as a pattern lying ON TOP
of a surface Latent (invisible) Patent (visible). Examples are
fingerprints, footwear impressions and tire tracks, among others.
Dust impressions are usually classified or defined as 2D impressions, Actually three dimensional having
very shallow depth and surface topology
General Characteristics of Impression Evidence
3D impressions
Object impresses its pattern into a softer surface, When tire makes
pattern in wet mud.
The famous impression of Neil Armstrong’s footwear impression on the moon is an example of a 3D impression
Large, diverse group, Expect at least one category present at most scenes. Fingerprints – most prevalent
Next would be footwear and tire impressions Bite marks (sexual assaults), lip prints and ear prints
comprise another category but occur much less frequently. Tool mark impressions is another large class of impression evidence that comprises several subcategories:
Screw drivers, saws, cutting tools (wire cutters) etc. Ballistics evidence:
Bullet impressions, Cartridge case impressions, and marks made by other
Impression Evidence
Bullet MarksCartridge Cases
Fingerprints
Footwear Prints
Tire Tracks
Tool Marks
Fired Weapon
Bite MarksEar Prints
Impressed printsShape of a toolStriated impressions or striated marks/scraping marks
Scrapping of tool’s surface against receiving surface
Categories of Impression Evidence
Footwear Impression Evidence
Refers to its future use; to help ascertain the truth of alleged facts. Footwear evidence = Associative evidence.
Helps investigators (police and prosecutors) and juries support contention that someone had been at crime scene.
Can identify which shoe left an impression ,,, can help place someone at the scene. ….
Alone, not determinative of guilt, Help circumstantially toward that end. Thus finding footwear evidence linked to an individual shoe can be
critical evidence, Used by a prosecutor during trial. Also helpful for investigators to understand the veracity of witness or a
suspect’s statements. Locating footwear evidence: not easy … logic can point to the location where
to search. Time and effort spent locating, photographing, lifting and comparing impression
evidence is critically important.
A Class of Associative Evidence
National Research Council of the National Academy of Sciences suggests that pattern (impression) evidence should be interpreted more carefully.
The report says that additional research is necessary in order to determine the underlying scientific basis of pattern evidence comparisons.
NRC committee also suggested there should be a statistical basis for making these comparisons, which currently, does not exist.
Practitioners do not universally agree that a statistical basis is necessary for making valid comparisons.
The NRC report does not say or imply that footwear comparisons are not valid nor does it say or imply that these comparisons have no forensic value.
National Research Council 2009 Report
Value of Impression Evidence
Links to Other Crimes
Minimum # of Perpetrators
Association with Other Evidence
Multiple impressionsAbsence of multiple impressions
Suggests a lone perpetrator
Backtracking footwear impressionsPath of perpetratorDiscarded weapons or other evidence
Associate footwear with tire impression - lead to a vehicle
Laboratory Examinations Establish LinksDatabase searching
Footwear impressions from various crimesUseful for investigations of repetitive crimes
BurglariesRecidivism rate is high >50%
ExampleBurglar enters a
house through a window and steps onto a carpet,
What is probability that dirt residue from sole will leave an impression?
Entering a House From the Outside
Defines residue type on shoe. Subsequent steps transfers
residue from shoe to carpet. Forensic value not known until
found and evaluated. Entry
Point 1
Entry Point 2
Assume two burglars enter scene at different points, Expect different footprints
‘Entry Points ‘1’ and ‘2’. If both footprints entering house at different locations had the
same sole pattern (class characteristics) Suggests @ least two people involved. Remote possibility that same person entered on separate
occasions. o Close examination of the size and other characteristics
might dispel that argument. Using the same logic, suppose a third unknown fingerprint was
found inside the house. Suggests a third perpetrator.
Hypothetical Murder Scene
Impression Evidence is Commonly Overlooked
Why Impression Evidence IsOverlooked or Not Found
Training
1. Not aggressively looking forBelief can’t be foundIncomplete understanding of value2. Incomplete search of sceneInability to find points of exit/entrance3. Lack of Understanding a Class of Fragile Evidence4. Lack of knowledge of How to Collect and Preserve
Scene
Other1. Initial Scene Responder Obliterates2. Public Obliterates Before Authorities Arrive
1. Weather Obliterates Outside Prints2. Surface Characteristics not Conducive to Production of Impression Evidence3. Scene Entrance Only Access to Scene
2D ImpressionsCommon but Overlooked
Types of 2D Impressions
Dry Residue Impressions
Wet Residue Impressions
Made from Dust Made from a Wet Slurry
2-D Impressions Impression transfers vary
Clean shoes leave impressions on paper/glass/countertops/furniture
Dirt and/or dust Wet grass Grease, oil, wax or furniture polish Blood or other fluids.
Visibility of an impression Contaminating material deposited
by shoe How it contrasts w/a surface
All impressions are potentially identifiable
Often, less visible impressions leave more detail
Most found on floor surfaces Magazines/newspapers, Tile floors Dust prints on carpets Shoe prints on doors Stepped-in
grease/oil/blood Requires careful
inspection/search of scene A category of fragile
evidence One of the first activities
ALWAYS Expect Impression Evidence. Study the Scene!!!!! What is the likelihood of finding probative impressions?
Where would they likely be? Are they wet or dry residue impressions Would they be plastic, latent, visible?
What is the strategy for archiving? Is it necessary to enhance them? Can they be lifted?
How should they be preserved?
Intellectual On-Scene Impression Evidence Checklist
Point of Occurrence Spilled BloodVictim’s Clothing
Areas of Struggle FurnitureFloorsStrewn reading material
Point of Entry/Egress WindowsAdjacent areas outside
Path Through Scene Struggle-to-Victim to Exit Point
Other Footwear Patterns On Doors – kicked in
OutsideLandscapingDriveways Walkways
Impression Prints @ Crime Scenes
Likelihood of Detecting 2D Footwear Patterns
Surface Wet Shoe Blood/oil/Grease Dry w/DustClean Dry
Carpet Unlikely Very Likely Likely Unlikely
Dirty floor Likely Very Likely Unlikely Unlikely
Clean unwaxed floor Likely Very Likely Very Likely Unlikely
Relatively clean unwaxed Likely Very Likely Very Likely Likely
Waxed desk top Likely Very Likely Very Likely Likely
Glass Very Likely Very Likely Very Likely Likely
Kicked in Door Very Likely Very Likely Very Likely Likely
Paper/cardboard Very Likely Very Likely Very Likely Likely
Bodziak: Footwear Impression Evidence, 2nd Ed, CRC Press, New York
Following Footprints Through the Scene
Using Technology
Finding Footwear Impressions2D Impressions
Flashlight – Oblique Lighting
RUVIS ALS
Mirror
Ultraviolet Infrared
Natural Light
Short & Long Wave
Oblique LightingLow angle light for impression evidence:Wet & dry residue footwear prints, tool marks, fingerprints
Camera
Light source
3D Impression Dry Residue PrintLight source
Camera
Wet & dry residue footwear prints, tool marks, fingerprints
The Mirror Technique
Enhancing & Archiving Impressions
Dust – General Considerations:
General term for solid particles with diameters less than 500 micrometers
Comes from the atmosphere – sources include:
soil dust lifted up by wind, pollution, volcanic eruptions, animals and people.
Composition of Dust and Soil
Human environment, e.g., Homes, offices, etc.,
Contain human skin cells, bacteria, plant pollen, human and animal hairs, feathers, textile fibers, paper fibers, minerals from outdoor soil,
Other materials, All come from the local habitat.
The quantity and composition of house dust varies greatly with seasonal and environmental factors:
Surroundings, exchange of outside air, age of the house, building materials and their condition quantity of furniture and carpets, state of preservation. ventilation, heating/cooling systems and habits of those living in the house.
House Dust
House dust consists of inorganic (minerals) and organic matter,
Relative proportions vary considerably. Dust from the homes with animals consists nearly
completely of organic material. In a study of 318 house samples, the proportion of
organic matter ranged between <5% to >95%. A survey of 11 homes showed
Organic content of house dust ranged between 25.7% to 56.5%,
Floor dust from seven offices had an organic fraction of 33%. Variances vastly different in different regions –
North, south, east, midwest, southwest, west. Rural or urban.
House Dust
Enhancing 2D Impressions - Overview
The current paradigm for enhancing dust impressions at crime scenes is
single dimensional … typically involves lifting or chemical tests to visualize the
mineral content of the dust.
Sort of a crap shoot.
The Logic of Enhancing Impression Evidence
Understand the likely content of dust at scene
Archive – Photography Determine type of Impression
Dry Residue Impressions Electrostatic Lifter Gel Lifter (Gellifter) On paper
o Chemistry (iron) Wet Residue Impressions
Gel Lifter Chemistry
o Fe: Ammonium Thiocyanateo Fe/Mg: 8-hydroxyquinolineo Oils: Iodine/benzoflavone or starch
Dustingo Black magnetic dusting powder
Superglue fuming
Electrostatic Lifting
Apparatus that creates static electricity between dust particles in the impression and a foil-backed Mylar film placed over the impression. If the print lifts, it is a dry residue print. That is, it was made from dust.
Footprint in Dust
Electrostatic LifterStun Gun
Foil-backedMylar Film Black Mylar Side
on Dust Print: Foil Side Up.
Electrode touching foil side
+Ground Electrode
Foil (silver) Side of Film
(up)
Black Side of Mylar
Film (down)
Electrodes
Arrows to Positive & Negative Electrodes
Fingerprint rollerTo Flatten Mylar
The set upMylar SheetFoil Side up
Lifted Footwear Impression
Place the metalized lifting film over the dust print. (dark side down)
Place the grounding plate about 8” next to the film.
Turn lifter so that the two metal probes on the back are resting on the grounding plate and the single probe is resting on the film.
Turn on the device and the film will be sucked down onto the print.
Gently brush over the film to remove any air bubbles.
Lift and you have your dust print.
Electrostatic Procedure
The issue of humidity studied by investigators employing a similar technique ESDA for the detection of indented writing. Studies show >>> humidity necessary … becomes detrimental when the relative
humidity goes above 98% at room temperature … quality drops off. At cold temperatures, even lower humidity causes a decrease in the quality of the
highlighted indented printing.
ESDA is not an electrostatic lifter, but the principle is the same, and one might expect similar deterioration of the quality of prints using an electrostatic lifter.
Generally, normal use of electrostatic lifter under normal conditions of temperature and humidity should provide reliable results.
HOWEVER … absence of humidity … ESDA process requires humidity … opens the possibility that the absence or near absence of humidity may also affect the quality of electrostatic lifts.
Effects of Humidity and Temperature
Electrostatic detection apparatus (ESDA)ESDA stands for Electrostatic Detection Apparatus. Used to produce a permanent 'lift' from paper which provides a visual map of indented impressions
Non-destructive. The paper under examination remains in exactly the same state, still available for other examinations.
Extremely sensitive - indentations found up to seven sheets below the page where the original writing was made.
ESDA works by stretching a Mylar film (like Clingfilm) over the document being examined. Mylar film is electrostaticaly charged. Where the paper is smooth, charging is generally uniform, however where
the fibers of the paper have been disturbed by paper-paper contact caused by indentations, the electrostatic charge is different versus the background.
Creates latent image. In order to visualize this latent image, Black toner similar to that used in laser printers is applied to the surface of the Mylar.
Toner preferentially sticks where the electrostatic charge congregates Areas of the indentations … an image with a grey toner background and
darker toner traces in the areas where there are indented impressions. Image is made permanent as a 'lift' by placing clear 'sticky backed plastic'
over Variables: Type of paper, the type of pen or stylus used, the number of
sheets of paper between the writing and the sheet holding the impressions, the humidity at the time the impressions were made, the humidity at the time the ESDA lift was made, the method by which the toner is put onto the Mylar film*, and the amount and direction of the electrostatic charge put onto the Mylar film.
Not suitable for the examination of loose fibred paper such as newspaper or very glossy paper such as magazine covers.
Liquid will completely destroy the ESDA impression. … fingerprint treatment should be done AFTER any ESDA examination.
Toner can be put onto the Mylar film using three methods: cascading tiny glass beads coated with toner over the surface, puffing an aerosol of toner powder over the surface or using a device similar to a powder puff to apply the toner.
Electrostatic lifts - fragile and must be protected.
Storing in flat boxes preserves better than other methods: Do not roll in tubes. A problem with flat storage is that dust is attracted to surface because the
lift retains a residual static charge – it stops the dust from falling off the Mylar film.
Problem exacerbated when lifts exposed to open air or in low-grade cardboard.
Even lifts stored in a high quality cardboard will lose residual charge over time resulting in the complete loss of the impression.
Storage conditions: High humidity increases rate of residual charge degradation Store with a desiccant (silica gel) taped to inside of box. Recommended to store the lifts so that the humidity does not exceed
50%.
Storing Electrostatic lifts
Differentiating Dry& Wet Residue 2D Impressions
Impression at Scene
Electrostatic Lift
Succe
ssful Unsuccessful
Dry Residue Impression Wet Residue Impression
Preserve Impression
Enhance
Photograph
Photograph
Chemical Enhancement
Magnetic Powder
Powder Suspension
PhotographProtect in Lift Box
Protect with Gel Lifter
If the print does not lift, it is a wet residue print. Advantage of electrostatic
lifting is preservation of the impression detail onto a black, Mylar surface.
What if, however, the impression does not lift? Is that proof that the impression was formed from a wet shoe?
Effective multi-tasking tools. Commercially available in two forms:
Rubber-backed gelatin-based in black, white or Clear gelatin on a clear backing.
Semi-sticky surface lifts dry residue impressions AND wet residue impression. Not reliable for differentiating between dry and wet
residue impressions.
Do not require static charge. “Sticky” surface “grabs” dust impression and sticks it to
the surface of lifter.
Also pick up any surrounding, contaminating material such as dust, which can mask the lifted impression.
Black Gellifter LiftingFootwear Impression
Gelatin Lifters (gellifters)
For preservation purposes, they serve a similar function as electrostatic lifters
For dry residue prints, the light tan color of the impression is nicely off-set by the black of the gellifter.
Like electrostatic lifters, gellifters can lift impressions from hard surfaces, paper, carpeting, clothing, etc. They are particularly useful on vertical surfaces.
Storage: In uncovered high quality cardboard boxes works well.
Generally recommended that low grade cardboard boxes not be used because … tend to shed fibers onto the lifted image.
Also, breathable boxes will keep condensation from forming on the lifts. Remove acetate sheet that comes with the lifter
Removing it later can remove some of the image.
Store the lifts in the same way as electrostatic lifts: high grade cardboard box without the acetate cover.
Over dusted or dense dust impressions can benefit from repeated removal of the acetate cover because this tends to remove some of the excess dust and render the lifted impression sharper.
Gelatin Lifters (gellifters)
Gellifter Type Characteristics Possible Uses 20
Black
Jet-black color and the high-gloss finish. The high-gloss provides for a reflection of light from the illumination source. Any light not reflected by the gelatin layer will be absorbed.
Traces picked up by the Gellifter, however, will reflect the light in all directions. The end result is a high contrast between the lifted material and the gelatin layer. Black finger print powders, lifted with a black Gellifter yield images that are sharp and rich in contrast.
-Footwear impression lifts-Fingerprint developed with:- Powders- Superglue- SPR-Fingerprints on some adhesive sides-Postmortem fingerprinting-Fingerprints on latex gloves-Improving old fingerprints
White
The gelatin layer of the white Gellifter absorbs blood and dyes from staining solutions.
The extreme white color of this Gellifter has a low fluorescence. Staining solutions which fluoresce when excited with green light (e.g., Hungarian Red) will therefore show up in high contrast to the gelatin layer.
-Fingerprints in traces of blood and traces in blood after chemical treatment-Fingerprints in staining solutions-Muddy shoeprints on nonporous surfaces stained with safranine O-Improving old fingerprints
Clear The transparent Gellifters have a clear polyester backing
-Fingerprints developed using powders – forms a positive print-Exemplar footwear impressions
Adapted from the BVDA gellifter brochure: http://www.bvda.com/EN/download/Gellifter_brochure.pdf,
Dry Residue Prints Dust or Dirt?
8-hydroxyquinoline Fluorescent reaction with iron, aluminum and
magnesium. Spraying the reagent in the dark (outside this is
difficult) gives yellow-white fluorescence that must be photographed immediately.
Testing the background before spraying the impression is critical
Testing a small part of the impression to see if the reagent is going to react with the dust/dirt present.
Chemical Enhancements of 2D Impressions
8-Hydroxyquinoline – UV Light
Bromophenol Blueand Bromocresol Green Chemical
Reagents
Chemical Enhancements of 2D Impressions
After Enhancement
Before Enhancement
After Water Vapor TreatmentJournal of Forensic Sciences, JFSCA, Vol.
41, No. 1, January 1996, pp. 23-26.
Oil or FatsIodine fuming
Iodine fuming followed by development with 7,8-benzophenone gives a blue/purple color.
First test a small part of impression and surface to see if the iodine is reacting.
Not a chemical reaction that takes place but more of an incorporation of the iodine into the matrix of the oil/fat.
Another way to visualize an iodine infused impression is to dust it with cornstarch and then hold a steam iron over the impression. The iodine will react with the starch to form a dark blue color.
Salt In the winter, tires running over roads salted with NaCl (sodium
chloride) will have the salt on the tread. Transferred to a surface over which the vehicle travels. Spraying the
impression with Silver Nitrate (AgNO3) will form silver chloride (AgCl) in those areas of the impression containing sodium chloride.
Shining a UV light or allowing sunlight to bake the impression will convert the AgCl to metallic Silver (Ago), which will appear dark gray or black.
Using Photography to Enhance Photographic sequence
important Establishing ( Midrange Close-ups (examination quality or
1:1) Record detail With & without scale – In the same
plane Need to make 1:1 enlargements Next to & parallel to print @ same
level as impression Made in plane of impression (vertical to
impression) Tripod is essential
Appropriate lighting Oblique ALS RUVIS
http://site.utah.gov/dps/impressions-fw-evidencecollection_000.htm
Camera Setup
Examination quality photographs should always be taken of both two-dimensional and three-dimensional footwear impressions
Photographs are taken for later comparison with known footwear A PROPER scale should ALWAYS be used when photographing footwear impressions
The scale should be on the same plane as the impression Objects with impressions should be removed from the scene if possible, AFTER examination quality photograph taken Always use a tri-pod Fill the frame of photograph with your impression including your scale Shade impression in sunny conditions Use side lighting from different angles take several shots
Photographing Footwear Impression Evidence
Proper Location of Light Source for 2-D Residue Prints
Light Source Should Be 4-5 Feet From Impression
From: Bodziak: Footwear Impression Evidence1
Existing Overhead Lighting
Oblique Lighting10 Degrees
Oblique Lighting45 Degrees
Oblique Lighting25Degrees
Ambient Light + External Source
From: Bodziak: Footwear Impression Evidence
High-Contrast B/W Photography
Film cameras High-contrast B&W film
Kodak Tech PanDigital Cameras
Use B&W setting Use software to convert
color imagesFilters
Subtract out the backgroundGray impression on red floor
Use red filter on camera Use UV or IR light ALS
Cross Polarization – Can Cut Glare
Polarizing filters can enable impressions to be photographed One filter in front of
oblique light source Other filter in front of
camera lens Rotate filters to achieve
max visibility of impression
Important technique for cutting glare
UV Light
UV wavelengths UV spectrum : 10-400nm
Long-wave: 320-400 Middle-range: 280-320 Below 200: not useful
Use Reflected short-wave UV light - RUVIS 18A filter over lens of camera
Filters out visible entering camera but not UV light
(Photos Rachel Leintz)
Unaided Eye Long Wavelength UV Image
http://www.ultravioletcameras.com/pdf/ETM-LongwaveUV.pdf
IR LightIR Spectrum
Useful portion: 700-900nm
Digital Camera altered for IR Use tungsten light
source - strong IR lightUse #87 filter over
camera lens to block all visible light
Enhancement of Bloody Footwear Impressions - Photography Using the ALS & Chemically
Photograph using ALS @ 535nm
Bloody Print On Terracotta TilePhotograph With Flashlight
Bloody Footprint Developed with Amido Black Protein Stain
Some blood enhancement chemicals work on only non-pourous surfaces (amido black), pourous surfaces (hungarian red), and some will work on both pourous and non-pourous (LCV). Once impression photographed, it can be collected.
This can be done by submitting the entire piece it was left on, or a gel lift can be used.
http://site.utah.gov/dps/impressions-fw-evidencecollection_000.htm
Choosing a Method for EnhancingLots of Choices
Need to understand the surface , How the method works Method’s limitations
StaticLift*
Gel Lift*
VWD SG/BY40 Mag. Black
Aluminum Black Powder
PowderSuspension**
Soil - Clay ---- + ++ ---- ---- ---- ++ ++Soil – Loam + + ++ ---- ---- ---- ---- ++++Soil – Chalk +++ +++ ++ ---- ---- ---- ++ ++Grass Stain ---- + ++ ---- ---- ---- ++ ++++Engine Oil ---- ++ ++++ ++++ ++++ ++ ---- ++WD40 ---- ++ ++ ++++ ++++ ++++ ++++ ++Baby Oil ---- ++ ++ ++++ ++++ ++ ++ ----Kitchen Fat ---- ++ ++++ ++++ ++++ ++++ ++++ ++++Diesel Fuel ---- ++ ++ +++ ++ ++ ++ ----Detergent ---- ++ ++++ ++++ ++++ ++++ ++++ ++++Dish Soap ---- ++ ++ ++++ ++++ ++++ ++++ ++Sprite ---- ++ ++ ++ ++ ++ ++++ ++++Diet Coke ---- ++ ++ ++ ---- ---- ++ ++Milk ---- ++ ++++ ++++ ++++ ++ ++++ ++++Beer ---- ++ ++ ++ ++ ---- ---- ++++Cider ---- ++ ++ ++ ++ ++ ++ ++++Dusty Shoeprnt
++++ ++++ ++++ ---- ---- ---- ---- ----
Wet Residue PrintsMade from wet shoes/bootsEnhancing depends on
Chemistry of recipient surface Chemistry of the impression Preservation technique
Powder Dusting Wet Residue Footwear Impression
Fingerprint powder (magnetic powder), can be used for collecting footwear evidence of WET ORIGIN. A wet origin impression is made when a wet shoe with dirt and debris walks across a solid surface such as tile or a wood floor. After drying, the dried impression is left. Use oblique lighting to find impressions.
http://site.utah.gov/dps/impressions-fw-evidencecollection_000.htm
Lifting Dusted Impression With White Gellifter
http://site.utah.gov/dps/impressions-fw-evidencecollection_000.htm
Because of soil components, we can enhance footwear Impressions chemically.
Best and most logical approachEmploy Chemistry in the laboratory instead of at
scene.
However, some scene circumstances may dictate chemical enhancement @ scene.
The result is either a colored or fluorescent impression, which can be photographed easily.
Chemical Methods
Enhancing Wet Residue Prints Technique Analyte
TestedProcedure Result
ExpectedAmmonium or Potassium
ThiocyanateFe Spray Red-Brown
8-hydroxyquinoline Fe, Ca, Al, others Spray Fluorescence under UV light
DFO Amino Acids/Protein
s
Treat gel-lifted surface @ 95oC
Fluorescence @ 515-535nm
Safranin O Oils Treat gel-lifted surface Fluorescence @ 535nm
Iodine Oils Fume in humidity followed by a benzophenone
soak
Blue/purple
pH of impression CaCO3 Spray or soak Blue
Superglue fuming Nucleophilic species
Fume after humidifying impression
Dust or stain developed impression
Checklist: Choosing method depends on following: Chemistry of the recipient surface. Chemistry of the impression Preservation technique
The chemistry of the surface critical to successful enhancement. If impression lies on a linoleum floor and the only resource is 8-
hydroxyquinoline, always the possibility that the surface will react with the reagent
Will mask the fluorescence of the impression. Check chemistry of the surface first - ensure that it does not react with
reagent.
The chemistry of the impression also critical Before treating impression determine whether the components in the
impression are going to react with the reagent and give the expected color or fluorescence.
Chemical Checklist
Preserving 2D Wet Residue Prints
Print dusted with magnetic powder Gel Lifted with White Gellifter
Alternative techniques Powder Suspension (WetWop – Iron Oxide) Iodine + benzophenone Iodine/starch Magnetic Powder
Bloody Footwear Impressions
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OJ Simpson Murder Case - 1994