Presentation on theme: "Print Development Methods"— Presentation transcript:
1 Print Development Methods Fingerprints Part IVPrint Development Methods
2 Fingerprints and DNA DNA from fingerprints. For DNA analysis to be successful, try to collect at least 100pg of DNAEach cell has about 6pgNeed about 100/6 = 16 cellsMost fingerprints have < 100pgOnly about 20% of fingerprints have sufficient amounts of DNA
3 Fingerprints and DNA Take Powder from Secondary Source Create Secondary Powder Source by removingPowder from original container to secondary containerBritish studied powder dusting on ability to obtain usable DNA profiles.Lifting using traditional lifting methods – tape and gels - does not quantitatively capture the DNA.After lifting, swab lifted areato collect remaining cellular material.Can still get DNA profiles using sensitive DNA analysis techniques from lift and swabs taken from the lifted area.Probably no relationship between amount of fingerprint residue present and amount of DNA present.Related to a person’s ability to shed cellular material.Referred to as sheddersTake Powder fromSecondary SourceOriginal Powder SourceSecondary Powder SourceSlim possibility of contaminating a fingerprint’s DNA with another after using the same brush and powder …Use clean brushes and fresh powder between dusting.Do not mix used and fresh dusting powder by releasing the used powder into the original reservoir.
5 Wet/dry Surfaces Small Particle Reagent (SPR) Suspension of molybdenum sulfide grainsSize of crystalline particles is criticalIn mild detergent solution (Kodak Photoflo or 1 drop of Dawn in Quart)Alternatives to molybdenumIron oxideemployed with varying successZinc carbonatetried on dark surfaces (particle size important)Some fluorescent compounds, tooTwo fingerprints on a car, developed with SPR.Works well on non-porous dry surfacesPlastic bags/wax paper/glass/painted surfaces/water-soaked firearmsAdheres to fatty components of latentUsed in a sequence approachUsed for items cannot be dried prior to processingUseful for sticky-side development
7 Vacuum Methods Vacuum metal deposition (VMD) – Columnar Thin Films (CTF) Smooth nonporous surfacesPlastic bags/plastic packaging material/smooth surfacesDrawbacksEquipment is expensiveSample chamber is smallProcedureVMD - Evaporates Gold and then Cd or Zn in vacuum chamberThin metal film deposited onto printCTF – Can work with other methods – Superglue fumingHow VMD WorksFingerprint ridgeVacuum Deposited GoldVacuum Deposited Zinc or Cadmium
8 Columnar Thin Film (CTF) Development A Measure of Topology Developed in 2009Lahktakia & ShalerColumnar Thin Films of Deposition Material onto Fingerprint residueThermal Evaporation of Deposition MaterialChalcogenide glassMgF2Gold/SilverAlQ3 – fluorescentTops of Columnar ColumnsLooking Down on CTF RidgeColumnsFingerprint Ridge
9 Requires Active Chemical Molecules in Print Residue Superglue FumingRequires Active Chemical Molecules in Print ResidueWaterAmino AcidsLactate
10 php?option=com_content&task=view&id=122&Itemid=49 Superglue FumingTwo methodsHeat & Humidity vaporization of superglueVacuum vaporization of superglueBox/iodinecafuming/tt-ck-fds.htmphp?option=com_content&task=view&id=122&Itemid=49
11 Heat & Humidity Super Glue Fuming Microburst Method of FBI
12 A: Fresh Clean Print B: 2- Day Oily Print FIG. 2—(A) SEM image of a fresh, cyanoacrylate fumed clean print at a 5000~ magnification; (B) SEM image of a cyanoacrylate fumed two-day-old clean print at a 5000~ magnification. The print was aged prior to fuming.Clean prints were prepared by thoroughly washing, rinsing, and drying hands, and swiping thumbs with ethyl alcohol. Oily prints were prepared by swiping a cleaned thumb across oily regions (forehead, nose, neck, or hair) prior to placing the print on the development medium.REFERENCE: Lewis LA, Smithwick RW III, Devault GL, Bolinger B, Lewis SA Sr. Processes involved in the development of latent fingerprints using the cyanoacrylate fuming method. J Forensic Sci 2001;46(2):241–246.
13 Images of the polymer formations developed 30 sec20 sec45 sec120 secImages of the polymer formations developedduring the cyanoacrylate fuming of a clean print.
14 Fresh Oily Print 2-Day Oily Print A: Image of a fresh, cyanoacrylate fumed oily print at a 5000~ magnification;B: SEM image of a cyanoacrylate fumed two-day-old oily print at a 5000~ magnification.
15 Vacuum Superglue Fuming Developed Watkin & Misner 1990Nat’l Res. Council of CanadaTechniqueLarge metal chamber with object to be printedWith small quantity of supergluePressure reduced to 200 mtorr (0.2 torr)Std atmospheric pressure 760 torr (760,000mtorr)Accelerates vaporization of superglueReduces time to deposit reduced about 20 min.CharacteristicsPrints translucent – weaklySharper ridge detail & more pore detailMore uniform printsLess risk of overdevelopmentVaporization can be used to develop prints not directly exposedInside of plastic bagsNot applicable to:Cans/bottles because they may explodeNothing wet
16 Visualizing Superglue Prints Super Glue Polymer has no significant absorption bandVisualizing Superglue PrintsDepends on color of objectChoose opposite to color of exhibit’s surfaceUsing LightALSWhite light or 450nm for initial examinationMay need oblique lightingReflective UV lightRUVISLight ridges against dark backgroundStaining – fluorescent dyesDusting – various powdersInstrumentationSceneScope - imager uses intensified UV reflectance instead of fluorescenceNot an ALS (Alternate light Source)Detects fingerprints (and footwear impressions) on most non-porous surfaces prior to any treatment or after cyanoacrylate fuming.
17 Visualizing Superglue Fumed Prints Enhancement with Fluorescent Stains Solvent for fluorescent stain is importantMust soften the polymerAllows penetration of stain without damaging the print imageWater rinse after stainingPreferred forNon-luminescent surfacesDark and/or multicoloredMost popular DyesRhodamine 6GArdrox 970-P10Basic yellow 40Mixtures of Dyes for colored surfacesStarDroxRAMNot suitable for:Porous surfacesSemi-porous surfaces
19 Always Assume Prints present on smooth AND the sticky-sides. Tapes are important because routinely used to seal boxes, letters and packaging.Also used to restrain people.Two distinct surfaces, each with unique development issues.Easy for fingers to stick to sticky side of tape - print impression transferred to tape.Latent print can be on smooth side of the tape.Developing fingerprints on the sticky-side of tapes has presented developmental problems. Traditional dusting powder does not work because it sticks to the adhesive and masks prints that might be present.Scientists and investigators developed variety of methods for developing adhesive-side prints.Must determine chemistry of sticky-side of tapesAffects subsequent print development.Rule of thumbTapes should be collected … preserved … taken to laboratory for print development … especially if tape stuck to itself.Rare instances when this is impossibleUn-sticking tape and developing the prints on-scene is necessary.
20 Adhesive Side Print Development Several techniques available or sticky-side of tapes:Small Particle Reagent (SPR),Black and white WetWop,Sticky-side powder,TapeGloTM ,TapeGlo is a fluorescent dyeGentian violet,Gentian violet (Basic Yellow 3): stains fats.Iron oxide powder-based suspension and othersPowder-based suspensions in a dilute detergent solution.No Technique develops prints on all adhesives all of the timeTape adhesives categorized: Rubber or acrylic-basedChemically, adhesives differ … why powder suspensions and chemical formulation development techniques work with one type of tape and not another.Masking tape represents a third category … Porosity creates problems for print development.
21 Spot Testing Adhesives Apply a toothpick-sized but clear spot of black or white powder suspension to a section of the tape that is less likely to have been handled.Wash the spot and only that area of the tape with tap water until the excess powder is gone.If powder remains on the spot, the adhesive is PROBABLY acrylic-based and should be developed using an aqueous version of Basic Violet 3 (Gentian Violet).If the tape is visible through after washing the test spot, it is probably a rubber-based adhesive and should be developed using powder
22 Tapes – Sticky Side Rubber-based adhesives – Use powder suspensions SPRWetWopIron Oxide suspensionAcrylic-based adhesives –Basic Violet 3WetWopSPR
23 TapeGlo™ TapeGlo™ : A fluorescent dye. Contains no hazardous or flammable liquidsNo fume hood is requiredShelf life is approximately six monthsPour TapeGlo™ into a dipping tray or spray on the adhesive surface.Fluoresces best when viewed between 488nm and 540nm.
24 Removing Tape from its Substrate Physical processes.Pulling apart:Fastest method … causes least damage to the underlying prints. Tedious and there is always the possibility of distorting the tape … alter underlying prints if surfaces – tape and surface – are tightly bound.Not recommended without a good reason.Cooling (Freezer)Many recommend cooling to un-stick from surfaces OR to un-stick them from themselves. … Freezing using liquid nitrogen or a microcircuit freezing spray. … Cool below the adhesive’s critical ‘glass transition temperature.’ … liquid nitrogen … dry ice. Adhesive solidifies … gently and slowly pulled from the surface or from the sticky-side of an adhering adhesive. Essentially the frozen adhesive ‘fractures’ from the surface to which it is bound.Freezer SprayTantamount to freezing. Electronics industry use these sprays … replace liquid nitrogen for separating adhesives from various surfaces … except from other adhesives. Temperature in the -65oF range, so precautions are necessary: wearing appropriate PPE: gloves, face mask, protective clothing.Solvents.Hydrocarbon-based solvents recommended for adhesives stuck to other adhesives: UnDoTM. Slow and tedious … use tiny amounts of solvent because too much will dissolve the adhesive and ruin prints.
25 Freezer Spray For localized, small areas of tape. Method of choice for removing adhesive tapes from plastic bags and other plastic material.Will freeze skin – use thermal gloves.Not for removing adhesive from paper, cardboard or from adhesives adhering to adhesives.Solvents:Removing adhesives from adhesives using solvents should be done carefully.Alternative method for disengaging adhesives from paper and cardboard and for separating adhesives from adhesives.
26 Super Glue for Adhesive Surfaces Low-level fuming (vacuum)Fluorescent stainingBasic Yellow 40 stainingRAMAn alternate for gentian violetSPR after SG fumingPowder dustingSticky-side DevelopmentVariable successType of tapeThicknessConsistency of the adhesiveEasily overdevelopedLoss of print detail & poor contrastSuper glue fume prints on the smooth side of tape before working on the adhesive side.Fingerprints on smooth side destroyed during cooling with Freezer Spray by condensationSuper glue fuming can develop prints on both the smooth and adhesive side of tapes.After developing smooth-side with superglue, photograph then liftThen use freezer spray.
28 Special Situations Bloody Fingerprints ConsiderationsDNAHow fingerprint made:Contaminated with blood or already on surface developed by the bloodPositive or negative print?Pre-existing sebaceous prints repel bloodSebaceous (greasy) printBlood repelled by ridges & accumulates in furrowsRidge detail may not be sufficiently defined for comparisonUse protein stain reagentMost do not interfere with DNA
29 Bloody Fingerprints Chemical Enhancement – Protein Staining Reagents ProcedureSprayed or squirted from wash bottle or immersionMay require de-staining using organic solventsProtein staining reagentsAmido Black 10B (Naphthol blue black B)Organic formulationImmersion 30 secondsWashing in organic solvents (methanol)Ethanol/water wash solution is field useableBlue/black stainsAqueous formulationCoomassie Blue R250Less hazardousCan be used with gel lifters after impregnating with dyePossible alternativesAcid Violet 17 (coomassie brilliant violet)Benzoxanthene yellow (luminescence in weak blood)Bloody fingerprint photographed on humanskin with the aid of an alternate light source.
30 Sequence Detection Prints in Blood Dark or ShinyBackgroundLightBackgroundObserve viaDiffused reflectionmodeObserve viaAbsorption (415nm)modeVisible as light ridgesAgainst dk. bkgrndVisible as dark ridgesAgainst light BkgrndDFOExamine inLuminescence ModeORProtein StainAcid Violet 17 or Amido BlackPhotography
31 Partial Bloody Print Developed with Crystal Violet (left) & CTF ® with Coomassie Blue