Presentation is loading. Please wait.

Presentation is loading. Please wait.

Print Development Methods

Similar presentations

Presentation on theme: "Print Development Methods"— Presentation transcript:

1 Print Development Methods
Fingerprints Part IV 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 Take Powder from Secondary Source
Create Secondary Powder Source by removing Powder from original container to secondary container British 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 area to 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 shedders Take Powder from Secondary Source Original Powder Source Secondary Powder Source Slim 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.

4 Specialized Physical Methods

5 Wet/dry Surfaces Small Particle Reagent (SPR)
Suspension of molybdenum sulfide grains Size of crystalline particles is critical In mild detergent solution (Kodak Photoflo or 1 drop of Dawn in Quart) Alternatives to molybdenum Iron oxide employed with varying success Zinc carbonate tried on dark surfaces (particle size important) Some fluorescent compounds, too Two fingerprints on a car, developed with 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

6 Vacuum Methods

7 Vacuum Methods Vacuum 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 Gold and then Cd or Zn in vacuum chamber Thin metal film deposited onto print CTF – Can work with other methods – Superglue fuming How VMD Works Fingerprint ridge Vacuum Deposited Gold Vacuum Deposited Zinc or Cadmium

8 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 Looking Down on CTF Ridge Columns Fingerprint Ridge

9 Requires Active Chemical Molecules in Print Residue
Superglue Fuming Requires Active Chemical Molecules in Print Residue Water Amino Acids Lactate

10 php?option=com_content&task=view&id=122&Itemid=49
Superglue Fuming Two methods Heat & Humidity vaporization of superglue Vacuum vaporization of superglue Box/iodinecafuming/tt-ck-fds.htm php?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 sec 20 sec 45 sec 120 sec Images of the polymer formations developed during 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 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 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

16 Visualizing Superglue Prints
Super Glue Polymer has no significant absorption band Visualizing Superglue Prints Depends on color of object Choose opposite to color of exhibit’s surface Using Light ALS White light or 450nm for initial examination May need oblique lighting Reflective UV light RUVIS Light ridges against dark background Staining – fluorescent dyes Dusting – various powders 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.

17 Visualizing Superglue Fumed Prints Enhancement 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 Dyes Rhodamine 6G Ardrox 970-P10 Basic yellow 40 Mixtures of Dyes for colored surfaces StarDrox RAM Not suitable for: Porous surfaces Semi-porous surfaces

18 Adhesive Tapes

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 tapes Affects subsequent 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.

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 dye Gentian violet, Gentian violet (Basic Yellow 3): stains fats. Iron oxide powder-based suspension and others Powder-based suspensions in a dilute detergent solution. No Technique develops prints on all adhesives all of the time Tape adhesives categorized: Rubber or acrylic-based Chemically, 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
SPR WetWop Iron Oxide suspension Acrylic-based adhesives – Basic Violet 3 WetWop SPR

23 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.

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 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.

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 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 Super 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 condensation Super glue fuming can develop prints on both the smooth and adhesive side of tapes. After developing smooth-side with superglue, photograph then lift Then use freezer spray.

27 Enhancing Bloody Fingerprints

28 Special Situations Bloody Fingerprints
Considerations DNA How fingerprint made: Contaminated with blood or already on surface developed by the blood Positive or negative print? Pre-existing sebaceous prints repel blood Sebaceous (greasy) print Blood repelled by ridges & accumulates in furrows Ridge detail may not be sufficiently defined for comparison Use protein stain reagent Most do not interfere with DNA

29 Bloody Fingerprints Chemical 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) Bloody fingerprint photographed on human skin with the aid of an alternate light source.

30 Sequence Detection Prints 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 OR Protein Stain Acid Violet 17 or Amido Black Photography

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

Download ppt "Print Development Methods"

Similar presentations

Ads by Google