2Forensically Important Surfaces NonporousSemi-porousCharacteristicsDo not absorb at allEmulsion deposit remainsUntil removedDegraded via environmental effectsFragileNWS Readily removed by organic solventsWSD readily removed by waterIntermediate characteristicsAbsorbs WSD slowlyMinutes to hoursNWSD remains on surface1 day to several daysSome NWS remains longerExamplesCertain plasticsWaxed surfacesVarnished wood& SomeWall paintsWall papersExamplesCertain plasticsGlassMetal surfacesGlazed ceramicsGlossy paintsNWS=Not Water SolubleWSD=Water Soluble Deposits
4Powder DustingGenerally used on nonporous surfacesLots of Choices
5Dusting Nonporous Surfaces Dusting powders used to develop fingerprints since the 19th centuryStudy in Great Britain showed that approximately 50% of their on-scene fingerprint identifications came from dusted fingerprints.Most ubiquitous technique for developing non-porous and selected porous surfaces,Experience : Black powder laden brush … swishing back and forth … bespectacled eyes leaning through a suspended black dust cloud … ridge detail slowly emerges through the haze.Growing list of dusting powders available from commercial suppliersComplicate the selection process.
6Dusting Nonporous Surfaces Powders are designed to solve surface-related problems … texture, porosity, color, cleanliness and etc.Most grouped into a relatively small number or categories depending on their chemical composition and particle size or shape.Specific formulation and characteristics that affect interaction with fingerprint residue, the surface, and its ultimate visibility.Limited, in-depth guidance concerning which powder to use in a specific circumstance.Many factors influence the success of powder dusting,Some not under the control of the scene scientist/investigatorNature and condition of the surface,Clarity of the ridge detailAge of the printEquipment. …Plethora of powders and powder brushes from which to choose,Examiner typically chooses one based onExperience with a particular product,Nature of the surfaceWord of mouthPreferences of a the crime scene unit.
7Print Dusting Powders Choice of Powder Common Powders Surface characteristicsColor of backgroundDetection MethodFluorescentVisualLocationPreservation MethodPhotographyLifting methodTapeGel lifterLiquid gel (Tex Lift)CastingCommon PowdersBlack powdersFerric oxideManganese dioxideLampblack powderWhite powdersTitanium oxideChalk-titanium oxideGray powdersChemist gray powderLead carbonate powderAluminum flake
8More Powders Organic powders KI/cornstarchCalcium sulfate/dihydrate cornstarchLuminescent (fluorescent & phosphorescent powdersAcridine orange & yellowCoumarin 6Crystal violetNile blueRhodamine B & 6GPhenothiazineLargely dependent on background colors & luminescent propertiesOther commercial preparationsPrints Developed with Fluorescent Powder
9Powder Characteristics Fluorescent – used commonly for currency/documentsSprayed in areas where thefts commonly take placeGood for multicolored papersMagnetic – Different formulationsTwo different preparationsCan have fluorescent additivesMagnetic applicatorsPowerful rare-earth magnetsPermanently magnetized steel rodsTextured surfaces – not vertical
10More Powders Metallic powders Thermoplastic powders Magnetic Fine lead Metallic flake powdersMetal evaporationGold/silver/aluminumThermoplastic powders
11When to Use Specific Powders Aluminum flake powdershould be used where ever possible and applied with a glass fiber brush.Zephyr style squirrel and tapered polyester brushesshould be used on surfaces where glass fiber brushes might tangle or clog because of surface contamination – dampness, grease or oil.Dust glass evidence with aluminum powder unless there is the possibility of contamination and tangling of the glass fiber brush.Black or jet-black magnetic powders should be used on textured surfaces.Black or jet-black magnetic powders should be used on u-PVC surfaces.All surfaces may respond better to chemical treatment, and this should be considered before embarking on a fruitless strategy.
12Powder Dusting Precautions Over dusting“Wash” by pressing lifter against print gentlyLifter removes excess powderToo much brushing smears ridgesSweaty or dirty fingers or made from someone with “firm” gripFriction ridges may spread outToo much sweat leaves a smudgePerspiration & grease on FP’s absorb into porous surfaces (paper/cardboard)Powders may not be successfulMagnetic brushes don’t leave excess powder
15Fingerprint Brushes & Smooth Surfaces Research: the HOSDB evaluated brushes used with aluminum powders on smooth surfaces.The study used aluminum flake powder for prints aged 24 hours to 7 daysglass, u-PVC, gloss painted wood (un-cleaned), gloss painted wood (cleaned) and painted automotive metal.Selecting the correct brush is important because if dusting is done incorrectly or with a heavy hand, the ridge detail can be obscured or destroyed .Un-starched glass fiber brushes superior to squirrel, polyester, nylon feather brushes, whether zephyr or artist mount.PrecautionsSlightly damp, greasy or sticky surfaces had problems. …Tendency of brush fibers to tangle.Squirrel zephyr type and & tapered polyester good alternatives because they are less prone to tangling.Brushing technique and found that spinning the brush caused glass fiber brushes to tangle more easily
16Textured SurfacesTextured surfaces present a challenge because powder particles can be trapped in the surface crevices.Generally two powders reflect the choice of most scene investigators:Aluminum flake and - BritishBlack granular powder - American investigators.Other choices available from commercial forensic supply sources,metallic powders, black, gray (dual), fluorescent, magnetic, bichromatic, powder formulation.Aluminum flake powder:Used where possible & applied with a glass fiber brush.Dust glass evidence with aluminum powder unless possibility of contamination and tangling of glass fiber brush.Black or jet-black magnetic powders should be used on textured & PVC plastic surfaces.Some surfaces respond better to chemical treatment,
17Magnetic Dustering Brushes Magnetic Dusting BrushMagnetizedBlack PowderBlack Magnetic Powder
19Lifting Developed Prints Powder liftsAfter developing and photographing, lifting is next step. The process, like many on-scene manipulations, is deceptively easy, but skill is involved.The skill is intellectual: Thinking through the SituationFirst consideration is surface.Surface TexturePrints on all surface types, and once developed, remain on that surface. One is the surface texture. The photographs illustrate the point.ab‘a’ Shows what appears to be a smooth wall in a home where fingerprints are suspected.‘b’ Shows the actual texture of the wall.
20Tape lifting was not the correct method. Fingerprint Dusting Powder On perfectly flat, smooth surfaces, tape lifting is the fastest and easiest for lifting dusted prints.Tape lifting does not usually lift the entire dusted printSome print detail stays behind, including some of the DNA.Problems with surface texture. Suppose tape was used to lift prints. When the lifted is transferred print to a fingerprint card and examined, you will see gaps in the friction ridge detail.Tape lifting was not the correct method.The result could be inability of latent print examiner to adequately compare the print.The undulating line (green) represents the wall, the black dots are the black powder dusted print ridges and the blue line is the lifting tape.The assumption is that the print penetrates part way into the depth (depending on pressure applied) of the textured surface. The dusted ridges also extend partway into the recesses of the texture.When lifting, the tape does not extend into the texture because it is fairly rigid and not easily moldable to textured surfaces. The result is a partially lifted print, where the only dust (print) that was lifted was where the tape came into contact with the powder on the higher surfaces.Fingerprint Dusting PowderFingerprint Lifting Tape
21Silicone (MikrosilTM ) Casting Mikrosil (silicone casting materials)works well on textured surfaces.Diagram below:The pliable silicone, (purple) conforms to the texture of the surface and engulfs the dust-developed print.When the silicone hardens and is removed, its adhesive forces (stickiness) entrap the dust on the print ridges and lift it intact.The lifted mold can be fixed to a fingerprint card to preserve it. Preparing the silicone casting material simply a simple matter of following the directions from the manufacturer.Mikrosil Covering Surface TextureFingerprint Dusting Powder
22Gellifters Gel lifters (gellifters) Commercially available in the form of rubber or acetate backed flexible gelatin.MalleabilityBetween tape and siliconeSufficient “give” and stickiness to capture ridge detail in the examples shown above but not if the texture runs too deep.Gellifters are black, white and clear,Choose gellifter by the color of the dusting powder,Should contrast well with the color of the gellifter surface.
23Tex-liftsTex-lifts are liquid glues that painted over the developed print.Liquid that captures ridge detail on slightly textured surfacesThe Tex-lift liquid is a light blue color that dries clear,Color of the powder is unimportant, as long as it contrasts with the surface.After the Tex-lift dries, capture print by lifting with lifting tape (or gellifter) andPlace onto a fingerprint lift card of an appropriate color.
25Powders for Textured & Difficult Surfaces Powder Characteristics Results of Study –On-scene ApplicationFlake Powders: Metallic flakeAluminumBrassMagenta FlakeMetallic flakes lie on surface of ridges - print appear reflective.Ridge detail appears continuousAluminum: most efficient on glass but works as well as alternatives on other smooth surfaces.Brass (bronze or gold): performs similarly to aluminum but should be used only on smooth silver surfaces where aluminum would have low contrast.Magenta Flake: can be an alternative to black magnetic for dark, textured surfaces.Black Powders: Granular carbon particles with other powders added to change the color.Jet blackGrayOther colorsRidge detail can be heavier around sweat pores giving a “granular” appearance.Black granular: To be used on some smooth surfaces onlyMagnetic Powders:Variations in color based on the addition of other powdersMagneticPowders come in two forms.1. Single component powderMagnetic particles act as the developing powder.2. Two component system Magnetic particles acts as a carrier for non-magnetic powderBlack magnetic: Most effective on textured and u-PVC surfaces. Other magnetic powders (gray, silver, etc) are not effective and are less sensitive. White magnetic is less sensitive by effective on dark surfaces.
27Developing Patent Prints in Blood Problem:Developing partial bloody fingerprint on concrete block painted white, glossy paint.Only the middle part of the print, approximately 1/3 of the ridge detail was visible, and it was in blood.Assume visible ridges in bloodPartial Bloody FingerprintStained with Coomassie Blue (Protein Stain)
28Superglue + Black Powder Dusting Partially bloody fingerprints on Stainless SteelDeveloped with Ni CTF (right)Compare with superglue + black powder(left)TraditionalSuperglue + Black Powder DustingNi - CTF
29Strategy OneDust the sebaceous secretions to develop the latent part of the print,Photograph the dusted print,Lift the dusted print using either tape or a gel lifterStain the patent part of the print using Acid Violet 17 or Acid Black 1 (Amido Black) for blood proteins.
31Strategy TwoFix the proteins in the patent part of the print using sulfosalicylic.Stain the blood proteins using Acid Violet 17 or aqueous-based Acid Black 1. Note: Using aqueous-based staining solutions run the risk of washing away DNA present. Using organic-based staining solutions run the risk of dissolving fingerprint emulsion that would preclude subsequent dusting.Photograph the developed patent print,Dust the print to visualize the oils in the latent part of the printLift using tape or gel lifter.
33Fingerprints and Heat: Fire Scenes Assume:Arsonists and terrorists handle accelerants, explosives and incendiary devices … these are considered fire and explosion debris. Incendiary devices … Molotov Cocktails … can have prints.Misperception:Fire and/or explosive environment destroys fingerprints.Research shows that fingerprints can persist at high temperatures, especially if carbon (soot) covers them.In experiments, fires purposely set with containers of a kerosene/gasoline mixture used to start the fire and then left inside the burning building.After extinguishing the fire using ordinary efforts, containers were recovered.Attempts to locate fingerprints on those items a few feet from the point of origin were unsuccessful.
34Fingerprints and Heat: Fire Scenes Rooms adjacent to the point of origin gave identifiable prints.Non-porous objects in or close to the point of origin rarely gave identifiable prints.Prints also can be found on incendiary devices,Body of literature is even scantier.How much heat can such fragile evidence withstand.Some studies have been designed to address this topic.
35Fingerprints and HeatFingerprints can withstand temperatures of at least 300o C.The recovery of useful marks coved by heavy soot deposits might withstand temperatures up to 700o C or more.Fingerprints in blood and the problem of how much heat they can withstand. Experiments suggest that blood prints survive heat up to approximately 200oC.Developing blood prints exposed 200 is a problem because none of the standard protein staining methods or presumptive blood tests workCatalytic tests fail at temperature below 150oC.Protein staining reagents might be successful at 200 CBlood forms a protective layer on the surface before flaking off which means that the surface oxidation between the ridge detail (blood covered ridges) and those non-protected areas (the grooves) is different.Processes sensitive to the surface conditions, e.g., Vacuum Metal Deposition, can develop prints where blood prints have been exposed to temperatures as high as 900oC.
36Locating Fingerprints at Arson Scenes Finding them should be a priority. Knowing where to look is the problem because items of potential evidence at arson scenes may be soot covered. One consideration is temperature.Gauge the hottest points at the scene and then confine collecting evidence in areas where temperatures did not rise above 300oC.Temperatures above 200o C destroy the organic components of the fingerprint residue, leaving inorganic salts, unless protected.Fire suppression.Water not usually detrimental to the oils in fingerprint residue because they are insoluble.If fire hot enough to destroy the organic components of exposed residue (>200o C), only inorganic salts will be left, which are soluble in water.Fire suppression efforts may dissolve these salts and efforts to develop prints will be futile.Metallic surfaces.There is the possibility that the print residue may act as resist against oxidation such that the unprotected metal might etch.Additionally, soot can protect fingerprints, which means that soot covered, potentially probative evidence should always be considered as potential sources of retrievable evidence.Soot causes problems in the laboratory because scientists must remove the soot without destroying the prints.
37Generally, Investigators Should Consider the Following. On-scene ActivityKnowledgeKnow the literature – Know where investigators reported success,Know the research … answered questions concerning the effects of temperature, accelerant, etc.Generally, Investigators Should Consider the Following.Less than 300o C … retrievableEvidence protected from direct exposure to heat and smoke may give retrievable fingerprints.Less soot covering fingerprints is better because the soot cover must be removed in the laboratory. Heavy soot deposits, however, does not mean removal techniques will not be successful.Dry evidence has a better chance of providing probative fingerprint detail than wet.Dried fingerprint residue … re-humidification may be successful, but the possibility of destroying the ridge detail is a concern.
38Fingerprint Development Method Use and LimitationsVisualizationExamine all items visually because heat & soot affect prints in various ways.Soot may preferentially deposit on oily surfaces.Heat may develop ridge detail on paper.Print residue can bake onto metallic surfaces.Black Powder Suspension (WetWop, etc)Best for non-porous surfaces <200oCBlack Magnetic PowderNot useful >200oCSmall Particle Reagent (SPR)Less useful than powder suspensionsSuper glue fuming + Basic Yellow 40Good up to 500oC on non-porous surfacesVacuum Metal DepositionLaboratory technique but appropriate up to 900oC. Water or dried water spots can interfere.Porous Surfaces: Protein/amino acid chemicals DFO & NinhydrinPerforms poorly when paper has been wetPhysical DeveloperDevelops prints on charred paper in laboratory environmentInfra-red imagingUseful for areas where charring & soot deposits: Use view finder of IR Camera. Use lens filter >715nm – RG850 filter.Blood Protein Stains (Acid violet 17, Coomassie blue, Amido black)Good up to 200 oCBlood Presumptive tests: Heme-specific StainsStops working >150oC