Fingerprints Part II C

1. Lecture 15-16 FingerprintsPart II C Print Development Methods

2. Fingerprints and DNA DNA from fingerprints. For DNA analysis to be successful, try to collect at least 100pg of DNA Each cell has about 6pg Need about 100/6 = 16 cells Most fingerprints have < 100pg Only about 20% of fingerprints have sufficient amounts of DNA

3. Fingerprints and DNA DNA from fingerprints. • Lifting fingerprints using traditional lifting methods – tape and gels - does not quantitatively capture DNA. • After lifting, some DNA remains • Swab area to collect remaining cellular material. • Although there is little possibility of contaminating one fingerprint’s DNA with another from after using the same brush and powder is slim, avoid the issue by using clean brushes and fresh powder between dusting. • Magnetic powder dusting reduces the chance of contaminating one fingerprint’s DNA with that of another. Do not mix used and fresh dusting powder by releasing the used powder into the original reservoir. • Fluorescent powders, although not usually recommended, can maximize an investigator’s ability to locate fingerprints having DNA evidence because of increased sensitivity. • Probably no relationship between the amount of fingerprint residue present and the amount of DNA present. • Related to a person’s ability to shed cellular material. The print residue is related to sweat gland activity. • Referred to as shedders

4. Specialized Physical Methods

5. Wet/dry Surfaces: Small Particle Reagent (SPR) Works well on non-porous dry surfaces • Plastic bags/wax paper/glass/painted surfaces/water-soaked firearms • Adheres to fatty components of latent • Used in a sequence approach • Used for items cannot be dried prior to processing • Useful for sticky-side development • Suspension of molybdenum sulfide grains • Size of crystalline particles is critical • In mild detergent solution (Kodak Photoflo) • Alternatives to molybdenum • Iron oxide • employed with varying success • Zinc carbonate • tried on dark surfaces (particle size important)

6. Vacuum MethodsVacuum metal deposition (VMD) – Columnar Thin Films (CTF) • Smooth nonporous surfaces • Plastic bags/plastic packaging material/smooth surfaces • Drawbacks • Equipment is expensive • Sample chamber is small • Procedure • VMD - Evaporates Au and then Cd in vacuum chamber • Thin metal film deposited onto print • CTF – Can work with other methods – Superglue fuming

7. Columnar Thin Film (CTF) Development A Measure of Topology • Developed in 2009 • Lahktakia & Shaler • Columnar Thin Films of Deposition Material onto Fingerprint residue • Thermal Evaporation of Deposition Material • Chalcogenide glass • MgF2 • Gold/Silver • AlQ3 – fluorescent Tops of Columnar Columns Columns Fingerprint Ridge

8. Superglue Fuming • Two methods • Heat & Humidity vaporization of superglue • Vacuum vaporization of superglue

9. Vacuum Superglue Fuming • Developed Watkin & Misner 1990 • Nat’l Res. Council of Canada • Technique • Large metal chamber with object to be printed • With small quantity of superglue • Pressure reduced to 200 mtorr (0.2 torr) • Std atmospheric pressure is @ 760 torr (760,000mtorr) • Accelerates vaporization of superglue • Reduces time to deposit reduced about 20 min. • Characteristics • Prints translucent – weakly • Sharper ridge detail & more pore detail • More uniform prints • Less risk of overdevelopment • Vaporization can be used to develop prints not directly exposed • Inside of plastic bags • Not applicable to: • Cans/bottles because they may explode • Nothing wet

10. Heat & Humidity Super Glue Fuming Heat & Humidity 80% Humidity Microburst Method of FBI

11. 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.

12. 30 sec 20 sec 45 sec 120 sec Images of the polymer formations developed during the cyanoacrylate fuming of a clean print.

13. 2-Day Oily Print Fresh 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.

14. Visualizing Superglue Prints • Super Glue Polymer has no significant absorption band • Illumination • Depends on color of object • Choose opposite to color of exhibit’s surface • Light ridges against dark background • ALS • White light or 450nm for initial examination • May need oblique lighting • Reflective UV light • RUVIS • Staining – absorptive characteristics of surface • Dusting • Instrumentation • SceneScope- imager uses intensified UV reflectance instead of fluorescence • Not an ALS (Alternate light Source) • Detects fingerprints (and footwear impressions) on most non-porous surfaces prior to any treatment or after cyanoacrylate fuming.

15. Visualizing Superglue Fumed PrintsEnhancement with Fluorescent Stains • Solvent for fluorescent stain is important • Must soften the polymer • Allows penetration of stain without damaging the print image • Water rinse after staining • Preferred for • Non-luminescent surfaces • Dark and/or multicolored • Most popular • Rhodamine 6G • Ardrox 970-P10 • Basic yellow 40 • Mixtures of Dyes for colored surfaces • StarDrox • RAM • Not suitable for: • Porous surfaces • Semi-porous surfaces

16. Adhesive Tapes

17. 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. • Important to ascertain sticky-side of tapes chemistry • of adhesive … affects subsequent print development. • Physical issues concerning collecting tapes and rendering them ready for print development. • Rule of thumb • Tapes should be collected … preserved … taken to laboratory for print development … especially if tape stuck to itself. • Rare instances when this is impossible • Un-sticking tape and developing the prints on-scene is necessary.

18. Adhesive Side Print Development • Several techniques available or sticky-side of tapes: • Small Particle Reagent (SPR), • Black and white WetWop, • Sticky-side powder, • TapeGloTM, • Gentian violet, • Iron oxide powder-based suspension and others • Powder-based suspensions in a dilute detergent solution. • TapeGlo is a fluorescent dye and • Gentian violet (Basic Yellow 3) is a solution that stains fats. • No Technique develops prints on all adhesives all of the time • Chemically, adhesives differ … why powder suspensions and chemical formulation development techniques work with one type of tape and not another. • Tape adhesives categorized: Rubber or acrylic-based. • Masking tape represents a third category … Porosity creates problems for print development. • Knowing the type of adhesive is first step … using incorrect technique ruins prints. • A spot test can easily and quickly identify correct procedural … Used to differentiate acrylic-based from rubber-based adhesives

19. 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

20. Tapes – Sticky Side • Rubber-based adhesives – • Use powder suspensions • SPR • WetWop • Iron Oxide suspension • SPR • Acrylic-based adhesives – • Basic Violet 3 WetWop SPR

21. TapeGlo™ • TapeGlo™ : • A fluorescent dye. • Contains no hazardous or flammable liquids • No fume hood is required • Shelf life is approximately six months • Pour TapeGlo™ into a dipping tray or spray on the adhesive surface. • Fluoresces best when viewed between 488nm and 540nm. http://www.forensicssource.com/ProductDetail.aspx?ProductName=1004023

22. 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 • 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 Spray • Tantamount 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.

23. Procedure for Using Freezer Spray • Use freezer spray on localized, small areas of tape. • Will freeze skin – use thermal gloves. • Not for removing adhesive from paper, cardboard or from adhesives adhering to adhesives. • Method of choice for removing adhesive tapes from plastic bags and other plastic material. • NOTE: • Super glue fuming is appropriate for prints on the smooth side of tape, and it should be done before working on the adhesive side. • Fingerprints on the smooth side will be destroyed during cooling because of the condensation that forms. • Super glue fuming can develop prints on both the smooth and adhesive side of tapes. • After developing the smooth-side prints with superglue, lift or photograph and then use freezer spray. • Disengagement of adhesives from adhesives using solvents should be done carefully. • An alternative method for disengaging adhesives from paper and cardboard and for separating adhesives from adhesives.

24. Super Glue for Adhesive Surfaces • Low-level fuming (vacuum) • Fluorescent staining • Basic Yellow 40 staining • RAM • An alternate for gentian violet • SPR after SG fuming • Powder dusting • Sticky-side Development • Variable success • Type of tape • Thickness • Consistency of the adhesive • Easily overdeveloped • Loss of print detail & poor contrast

25. Arson Scenes • Fingerprints survive heat • Prints covered by soot • Prints generally available up to 900 deg F

26. Enhancing Bloody Fingerprints

27. Special SituationsBloody Fingerprints • Considerations • DNA • Heavily stained areas w/o ridge detail • Finger contaminated with blood or latent already on surface developed by the blood • Preexisting latent prints repel blood • Blood does not visualize eccrine latent prints • May reveal sebaceous (greasy) print • print will be reversed-blood repelled by ridges & accumulate in furrows • Ridge detail not usually sufficiently defined for comparison • Use blood fingerprint enhancement reagent • Most do not interfere with DNA

28. Bloody FingerprintsChemical Enhancement – Protein Staining Reagents • Procedure • Sprayed or squirted from wash bottle or immersion • May require de-staining using organic solvents • Protein staining reagents • Amido Black 10B (Naphthol blue black B) • Organic formulation • Immersion 30 seconds • Washing in organic solvents (methanol) • Ethanol/water wash solution is field useable • Blue/black stains • Aqueous formulation • Coomassie Blue R250 • Less hazardous • Can be used with gel lifters after impregnating with dye • Possible alternatives • Acid Violet 17 (coomassie brilliant violet) • Benzoxanthene yellow (luminescence in weak blood)

29. Sequence DetectionPrints in Blood Dark or Shiny Background Light Background Observe via Diffused reflection mode Observe via Absorption (415nm) mode Visible as light ridges Against dk. bkgrnd Visible as dark ridges Against light Bkgrnd DFO Examine in Luminescence Mode Photography Protein Stain or DAB

30. Partial Bloody Print Developed with Crystal Violet (left) & CTF ® Partial Bloody Print Developed with Coomassie Blue