Latent Fingerprint Powder

3 Types of Brushes:

Zephyr Brush - Fine fiberglass filaments

Camel hair - cannot twirl
Squirrel Hair - cannot twirl

4 Basic Brush Strokes:

1. Painting - locates print with side to side motion
2. Swirling - circular motion with wrist
3. Twirling - Smaller circles by twisting brush between fingers
4. Dabbing - Straight into powder and then into the print

• After putting tape over print, run an eraser over the tape to eliminate air bubbles obscuring the impression
  
• Hold tape with both ends when lifting from a surface to prevent curling and sticking of loose tape
  
• Always fold the torn tape end on the dispenser to save time peeling between each use
  
• Huff onto the print if it needs moisture with your breath
• Cut the loose ends of tape off of the fingerprint card and sign 1/2 on tape and 1/2 on the card to prevent forgery

Surfaces for fingerprint Powder
NON-POROUS surfaces: sliding glass door, automobile exteriors, counter-tops, t.v. sets, metal filing cabinets, painted doors, mirrors, broken glass, metal window frames, plastics, glass, metal, smooth surfaces and objects etc.

Magnetic Powder

• Magnetic Brushes do not have whiskers. A magnetic release button collects and releases the magnetic powder
• Same 4 brush strokes as regular fingerprint powder
• The brush does not touch the print, only the powder suspended from the magnet makes contact with the surface

Tips:

• The first sweep of powder over the print will be the darkest, and all secondary sweeps will lighten the developed print
• Best on porous surfaces as non-magnetic would pack into textures
• NEVER use magnetic powder on surfaces above the eyes. Either raise your level, or use non-magnetic. The metal fragments could cause blindness, especially if rubbed in deeper.
  

Surfaces for Magnetic Fingerprint Powder
POROUS surfaces, NO METAL: textured surfaces, vinyl imitation leather, lightly textured automobile dashboards, lightly textured door panels, raw wood, paper, cement, shiny magazine covers, boxes with coated surface, some plastic materials, food storage containers and plastics etc.

Sudan Black

• Is for greasy, sticky and waxy surfaces (bag of potato chips)
• Is mixed with methanol, the alcohol evaporates and only the Sudan Black stain remains
• Non-porous surfaces - glass, metal, plastic and the inside of latex gloves
• can be on wet or dry surfaces
• reacts with the lipids/fats to develop print

Procedure:

1. Using a tray, immerse item in Sudan Black for 2 minutes
2. cold tap water rinse - removes excess dye
3. dry item at room temperature

Small Particle Reagent (SPR)

• Used when item is wet or on wet surfaces
• More commonly used over Sudan Black
• Reacts with Lipids/fats
• Non-porous surfaces
• Can be sprayed using a spray bottle, a compressed-air spray system, or dipped if small enough
• SPR is Molybdenum Disulfide MoS₂
• 'Dabbing' powder technique best used with this technique

PROS -

• Easy cleanup - soap and water
• Can be used underwater
• Immediate reaction

CONS -

• Very messy
• Stains
• Needs gloves and safety glasses

PROCEDURE:

1. Spray print with SPR [mix 1 ounce of MoS₂ + quart of water + 2-3 drops PhotoFlo]
2. Rinse with water
3. Only the MoS₂ remains on print
4. Photograph print
5. Dry
6. Lift print

Iodine Fuming

• Works Immediately
• Reacts with Lipids/Fats through physical attraction
• Reaction: Physical Attraction
• Do not inhale fumes - Fume Hood or ventilated area. Harmful to mucous membranes
• Porous and Non-porous surfaces

3 Types of Application:

1. Gun
2. Plastic Container
3. Shake & Bake Method - Shaking crystals on top of paper

CONS -

• Toxic
• Corrosive
• Allergic Reactions

PROS -

• Easy to use
• Cheap
• Easy to build gun
• Easy to transport
• Reusable (Iodine crystals, drie-rite)
• Can be used repeatedly on paper
• Any surface that isn't wet
• use on dead people
• can be made permanent using Spray Starch or Huffing
• can be for any size
• non-destructive - does not inhibit other techniques

Sequencing Order of Techniques:

1. Alternate Light Source (ALS)
2. Iodine Fuming
3. DFO
4. Ninhydrin
5. Physical Developer - last resort

Procedure:

1. Prepare photo settings since developed print fades quickly
2. Pass fumes over surface of print
3. Photograph developed print immediately

Diazafluoren-9-One (DFO)

• Develops 2.5x more prints than Ninhydrin
• Flammable - used in film hood, full-face mask, gloves
• Reacts with Amino Acids in fingerprint
• takes 24 hours to process without oven/hair dryer to accelerate development
• cannot be used on previously wet items (washes off amino acids)
• Shelf life - 6 months
• More sensitive to amino acids than Ninhydrin

When to use DFO over Ninhydrin?

Since Ninhydrin dries purple, use DFO on dark, purple or busy backgrounds

PROCEDURE:

1. Submerge or spray item 5 seconds
2. Dry item in fume hood
3. Repeat process steps 1 & 2
4. Dry or Accelerate with oven or hair dryer [@ 50-100°C 10-20 minutes]
5. MUST use Alternate Light Source (ALS) [495nm-550nm]
6. Red Filter (610nm-700nm) Bulb Setting 1½ - 2

Ninhydrin

• Porous surfaces
• 95% of fingerprints on paper are developed with the Ninhydrin technique
• delayed 24 hours - 10 days to develop
• reacts with Amino Acids
• Is cheaper than DFO
• Cannot use on items that have been wet (amino acids are water soluble)
• Previously referred to as Rheuman's Purple
• Develops Purple

3 Alcohol Ninhydrin options:

1. Acetone - dissolves ink
2. Methanol - dissolves ink
3. Heptane - do not inhale

3 Ways to Use Ninhydrin:

1. Spray bottle
2. Dipping - 3 to 4 dips into alcohol
3. Painting onto a surface

PROCEDURE:

1. Immerse in tray 5 seconds, spray or paint until saturated
2. Photograph after developed with green filter
3. Photograph under ALS with orange or red filter if required

Physical Developer

• Used on Porous Objects
• Reacts with Lipids/Fats, Oils, and Waxes
• Only technique useful on currency
• Cannot be used on metal (interrupts ionic suspension) or Thermal/carbon paper
• Bad for grooves/folds on paper. Seeps and stains them
• Will overdevelop if soaked too long and become solid black
• Develops quickly
• Only develops ~25% or prints
• Cannot use any other techniques after Physical Developer. LAST RESORT

LAST IN SEQUENCING ORDER

1. Alternate Light Source (ALS)
2. Iodine Fuming
3. DFO
4. Ninhydrin
5. Physical Developer

PROCEDURE:

1. Pre-Wash (10 min) 25 grams Maleic Acid mixed + 1 Liter of Distilled Water (removes dyes in paper)
2. Working Solution (20 min)- 3 part solution [carrier + Detergent + Silver Nitrate]
3. Rinse (5 min) Stop-bath of Distilled Water
4. Rinse (5 min) Bleach solution wash [50/50 Distilled water + Bleach] bleaches background, not print

Crystal Violet

• Used to develop fingerprints on Adhesive Surfaces
• Reacts with sebaceous Lipids/Fats
• Stains proteins from dead skin cells
• Opaque, dark background staining is main concern from technique
• Effectiveness varies depending on type of tape/adhesive surface
• If tape is on glass, Freeze the tape before removing to prevent damage to fingerprint
• best on Non-Porous surfaces
• Stains. Wear gloves
• Develops Purple
• Also known as 'Gentian Violet'

(Clear Tape)

Types of Application:

1. Dipped

(Duct Tape)

PROCEDURE:

1. Immerse/Dipp in solution for 1-2 minutes. Wear gloves!
2. Cold water tap rinse 30 seconds
3. view with ALS if required using red goggles
4. Dry.
5. Photograph. Print is not lifted to prevent damage.

Sticky-Side Powder (SSP)

• Used on Adhesive Surfaces
• Background staining is main concern, same as Crystal Violet
• Reacts with Lipids/Fats
• If tape is on glass, freeze it before removing to prevent damage. Same with Crystal Violet (CV)
• Also known as Lightning Powder and Wetwop
• Used on Non-porous surfaces
• Develops Dark Gray

(Clear Tape)

Type of Applicaton:

1. Brushed or Painted on

(Duct Tape)

PROCEDURE:

1. Brush adhesive surface with modest amount of Sticky-Side Powder and Water mixture until fully coated
2. Cold tap water rinse 30 sec
3. dry
4. repeat if developed too light
5. Photograph. Do not lift to prevent damage.

(Masking Tape)

Cyanoacrylate (Superglue)

Superglue Technique

• Requires chamber for development (Fish tank, automobile)
• Non-Porous surfaces
• Develops white
• If using accelerant, caution: evidence is HOT when removing. Wait until reaction is complete and cooled down.
• Superglue is mostly attracted to old superglue. Keep chambers clean.
  

(Trash Bag)

4 Steps to Cyanoacrylate:

1. Evaporation
2. Containment
3. Absorption
4. Polymerization - turns print into plastic

Types of Cyanoacrylate Methods:

• Regular - no accelerant
• Accelerant - Hot Shot: cotton ball drenched in Baking Soda (Sodium Bicarbonate) + Water + few drops of liquid Cyanoacrylate
• Gel pad
• Vacuum

Accelerant with Hot Shot

Heat Accelerant + Gel Pad

Vacuum Chamber

PROS -

• Effective results
• simple to use
• low cost

CONS -regular

• Messy
• Slow (2 hours to 2 weeks) if without accelerant
• Not practical for field use

CONS (with accelerant) -

• Caustic chemicals - irritates mucous membranes and eyes
  
• Short shelf life
• Rapid burst of fumes
• Not cost effective

CONS (with hotplate)

• Messy
• Not practical for field use
• overdevelopment is a concern

Cyanoacrylate INCOMPATIBLE with:

• Iodine Fuming
• Ninhydrin
• Porous surfaces

PROCEDURE:

1. Place items into sealed chamber. Add glue
2. Add humidity source. Cup of warm water for smaller chamber and multiple liter containers of water for automobiles. Size of water source dependent on area of chamber. Keep water 3" from evidence.
   
3. Fume at least 10-30 minutes for 10 gallon fish tank depending on use of accelerant. 20-40 minutes for gel, 2-4 hours for automobiles.
4. Remove and study under oblique lighting. Vacuum method may require oblique lighting.
5. Ventilate and Photograph.
6. Dye print. If powder is used, use AFTER photography to prevent damage to print.
   

Ventilation:
rooms - 30 minutes
cars - 10 minutes
small chambers - 2 to 3 minutes

Recommended Surfaces: metals, leathers, purses, plastics and plastic bags, cash drawers, vinyl, aluminum cans, rubber, gun grips, electrical tape, colored paper, glass