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