Advanced Fingerprint Development Flashcards
What are the three types of fingerprints??
Latent
Patent
Plastic
What are latent fingerprints?
Prints that are invisible or undetectable.
What are patent prints?
Visible prints.
What are plastic prints?
3D impressions
What is the general rule regarding suitability of surfaces for fingerprinting?
Fingerprints may be found on any surface with sufficient size and surface continuity to record the necessary ridge characteristics in sequence.
3
What characteristics of surface should be considered when deciding on a fingerprint development technique?
- Porous/non-porous/semi-porous
- Colour
- Wet or dry
What types of things should be considered when deciding on a fingerprint development technique?
3
- Surface
- The technique itself
- Does the technique meet the Daubert threshold criteria
What is a porous surface?
A surface that absorbs fingerprint residues.
Give examples of porous surfaces.
4
Paper
Cardboard
Wood
Tape
What are non-porous surfaces?
Surfaces that do not absorb/resist fingerprint residues.
Give examples of non-porous surfaces.
4
- Glass
- Metal
- Plastic
- Tape
What are semi-porous surfaces?
Surfaces that both resist and absorb fingerprint residues.
Give examples of semi-porous surfaces.
4
Glossy cardboard
Magazine covers
Leather
Finished wood
What characteristics of development techniques should be considered when determining the appropriate technique to use?
7
- Environmental conditions
- Destructive or non-destructive
- Interferences with subsequent testing or processes
- Examiner preference or comfort
- Safety and scene limitations
- Transportable
- Premixed vs. mix your own
When using a fingerprint development technique, which is preferred: Pre-mixed or DIY?
Mixing fresh
What is the Daubert threshold criteria a forensic technique must meet?
4
General acceptance within the scientific community
Peer review
Publication
Relevant
Outline the composition of a fingerprint.
3
Eccrine sweat
Sebum
Foreign materials
What are the three sources of natural secretions on the human body?
Eccrine sweat glands
Sebaceous sweat glands
Apocrine sweat glands
Where are eccrine sweat glands located on the body?
Palms of hands and soles of feet
Where are sebaceous sweat glands located on the body?
Areas covered by hair.
Where are apocrine sweat glands located on the body?
Armpits/groin
Outline the composition of eccrine sweat.
98.5% to 99.5% water
0.5% to 1.5% solids
Outline the compositions of solids in eccrine sweat.
1/3 to 1/2 inorganic salts
1/2 to 2/3 organic substances
What do inorganic salts in eccrine sweat consist of?
4
Cl, Br, I, F
What does inorganic salt concentration in eccrine sweat depend on?
5
Rate of sweating
Duration of sweating
Frequency of sweating
Salt intake
Climate
What does the organic component of eccrine sweat consist of?
4
Amino acids
Fatty acids
Ammonia
Urea
What does sebum mainly consist of?
3
Saturated fats
Waxes
Squalene
What is squalene?
An organic compound.
What about sebum makes it significant when it comes to fingerprinting?
Affinity to fingerprint powders.
Give examples of common amino acids found in eccrine secretions.
7
Serine
Lysine
Aspartic acid
Glutamic acid
Ornithine
Glycine
Citrulline
Give examples of fatty acids commonly found in sebaceous secretions.
5
Palmitoleic acid
Oleic acid
Palmitic acid
Stearic acid
Myristic acid
How much of sebaceous secretions are made up of squalene?
12%
Give some examples as to why a forensic identification officer may use chemical development for fingerprints.
5
- Can be more sensitive than powders
- Chemicals used with light sources can yield more impressions
- Older exhibits can be examined
- Porous and non-porous
- DNA contamination through fingerprint brushes
What type of reagent is DFO?
Amino acid reagent
What is the chemical name of DFO?
1,8-Diazafluoren-9-one
When was the first application of DFO?
1950
When was DFO first applied to forensic field work?
1990
What colour are fingerprints developed with DFO usually visualized as?
Magenta
Does DFO fluoresce under ALS?
Yes
At what point of sequential processing should DFO be used?
First
Which is more sensitive: DFO or ninhydrin, and by how much?
DFO is 2.5 times more sensitive than ninhydrin
What types of surfaces is DFO suitable for?
Porous
Outline the process of development with DFO.
6 steps
- Spray, dip or brush exhibit twice
- Air dry
- Repeat
- Place in dry oven at 100 deg C for 10 mins
- Record/photograph results
- View under green light with orange or red barrier filter.
Describe the appearance of DFO
Clear and colourless
How do you photograph prints developed with DFO?
Orange barrier filter and green light (505, 532 nm)
What type of reagent is 1,2-Indanedione/Zinc Chloride (IND/Zn)?
Amino acid reagent
As of what year is IND/Zn new?
Sept 2006
When was the first application of IND/Zn and by who?
1997 by Ramotowski et al
What two reagents did IND/Zn begin to replace?
DFO and ninhydrin
How much more sensitive is IND/Zn over DFO?
10 times more sensitive
Describe how IND/Zn looks.
Clear and colourless
On what type of surfaces is IND/Zn effective?
Porous surface
Outline the process of development with IND/Zn.
4
- Immerse exhibit for 5 seconds (double dip method preferred)
- Allow to air dry
- Place in sealed dry mount press at 160C between two sheets of paper towel for 10 seconds
- View with green ALS and orange barrier filter
What does an exhibit processed with IND/Zn look like?
Produces pinkish colour that is slightly darker than DFO.
How do you photograph an exhibit processed with IND/Zn?
Orange barrier filter and green light (505, 532)
What colour will a fingerprint processed with IND/Zn fluoresce as?
Yellow
What type of reagent is ninhydrin?
Amino acid reagent
When was the first application of ninhydrin?/
1910
When was ninhydrin first applied to forensic fieldwork?
1954
What part of the sequential process is ninhydrin?
Second following DFO
Describe how ninhydrin looks.
Clear and colourless
On what types of surfaces is ninhydrin effective?
Porous
What colour do fingerprints processed with ninhydrin appear?
Ruhemann’s Purple
True or false: Ninhydrin stops developing seconds after application.
False, it can continue to develop over several weeks
What could make ninhydrin fade?
Exposure to UV
On what porous surface is ninhydrin ineffective?
Previously wetted paper
What can ninhydrin-developed prints be treated with for fluorescence?
Zinc chloride
Outline the process of ninhydrin development.
3
- Spray, dip or brush exhibit
- Air dry
- Place in humidifying cabinet at 80C with 65% relative humidity
What is an accepted alternative if a humidifying cabinet is not accessible for ninhydrin processing?
Kettle
How are prints developed with ninhydrin photographed?
No filter, white light
List the amino acid reagents discussed in class.
3
Ninhydrin
IND/Zn
DFO
What type of reagent is Oil Red O?
Lipid reagent
What colour does Oil Red O stain lipids?
Red
How do fingerprints processed with Oil Red O appear?
Dark red
On what type of surfaces is Oil Red O effective?
Porous substrates that have been previously wet.
Outline the process of Oil Red O processing.
6
- Immerse exhibit into solution
- Fingerprints should begin to appear within 5 minutes but older or weaker impressions may take longer
- Leave item in solution for 60-90 mins
- Remove item and drain
- Rinse item in buffer solution
- Let air dry
How are exhibits processed with oil red O photographed?
White light, no filter.
Outline the sequential processing best practice for porous surfaces.
4
- Light - white, blue, green, laser
- Indanedione/DFO
- Ninhydrin
- Physical developer or Oil Red O
Why can’t previously wet exhibits be processed with amino acid reagents?
Amino acids will have been washed away
What is cyanoacrylate fuming?
5
- Heat is applied to super glue
- Glue vaporizes
- These vapours are extremely sensitive to fingerprint residues
- Vapor polymers plasticize the residues, appearing white in colour
- Can be enhanced with dye stains
What are the two methods for CA fuming?
Fuming wand
Commercial fuming cabinet
How does a fuming wand work?
Butane torch with brass cartridge infused with CA and steel wool attached
As cartridge and glue is heated, it vaporizes
How does a commercial fuming cabinet work?
4
Heating boats for glue and water
120C, 80% relative humidity
Air circulates within chamber, vapourizing glue
System purged when process is complete, preventing overdevelopment.
Give an example of a commercial fuming cabinet.
Cyanosafe
Give examples of dyes that can be used to stain prints developed via CA fuming.
4
Rhodamine 6G
Ardrox
Brilliant Yellow
Basic yellow
What type of light and filter is required to visualize Rhodamine 6G?
Laser (532 nm)
Orange filter
What do exhibits stained with Rhodamine 6G need to be rinsed with?
Methanol
What type of light and filter is required to visualize prints stained with Ardrox?
UV light (350-380 nm)
No filter required
What should exhibits stained with Ardrox be rinsed with?
Water
What light and filter should exhibits stained with brilliant yellow be viewed with?
450 nm ALS
Orange filter
What should exhibits stained with brilliant yellow be rinsed with?
Water
Outline the sequential processing best practice for non-porous surfaces.
3
- Light - white, blue, green, laser
- CA, examine with white light
- Dye staining, examine with appropriate ALS
If a porous item has been wet, what lipid-reacting chemicals can be used in sequential processing?
3
Iodine fuming
Small particle reagent
Powder suspension
What is a hazard of iodine fuming?
toxic
What is vacuum metal deposition and how does it work?
3
Utilizes gold and zinc to visualize impressions
Gold is evaporated in a chamber and adheres to entired substrate and diffuses into the residue of the impression
Zinc is evaporated and attaches to gold.
On what type of surfaces is vacuum metal deposition useful?
Semi-porous surfaces
What techniques can be used for developing latent prints on firearms, cartridge casings and spent cartridge casings?
7
CA
Dye staining
Forensic light sources
Camphor smoke development
Gun bluing
Fingerprint powder
VMD
Describe the process of using Gun Blue on cartridge cases.
3
- Pour bottle contents into glass receptacle
- Submerse case into solution and let develop for ~10 s
- Quickly remove case and place into bath of distilled water
Why are cartridge cases placed in distilled water after development with Gun Blue?
Stops development
Is subsequent processing required after processing a cartridge case with Gun Blue?
No.
How do friction ridges treated with Gun Blue appear?
Dark blue-black colour
Under which lighting can fingerprints developed with Gun Blue be visualized?
Room lighting
What is thermal paper?
Paper with one or two thermally active sides that form images when printed, via heat
Give examples of thermal paper
2
Receipts
Fax paper
How do traditional fingerprint development techniques interact with thermal paper?
Often turn the paper black as amino acid reagents react unfavourably with the chemical treatments applied to the paper during manufacturing.
What development methods can be applied to thermal paper?
6
Steam
Dry heat
Magnetic powder
Acid fuming
Sandwich technique (indanedione)
Acetone wash
Outline the direct steam technique for developing fingerprints on thermal paper.
Receipt held 2-5 inches above the steam head and moved slowly from side to side to develop the entire receipt.
What is the reaction that takes place for the direct steam method?
Reaction with unsaturated lipids like unsaturated fatty acids and squalene.
For how long after deposition can the steam technique effectively develop fingerprints?
4 weeks
True or false: The steam technique is on par with other techniques like ninhydrin & DFO, fuming, Oil Red O.
True
Which is preferred in the steam method: Direct or indirect steam
Direct
What common household appliance can be used to develop fingerprints on thermal paper?
Hair dryer
Give examples of fuming techniques for thermal paper.
2
Hydrochloric acid fuming
Acetic acid fuming
Describe the sandwich technique of fingerprint development on thermal paper.
4
- Treat two pieces of absorbent paper towl with 1,2-indanedione
- Place paper exhibit between treated paper towels
- Seal in Ziploc bag
- Place bag in oven at 80C for 20 minutes
List some factors that could affect your results when developing prints on receipt paper.
6
- Where the receipt is from
- Who touched it
- Time between touching and processing
- Environment
- Materials available in lab
- Not all receipt paper is thermal
List reactants used for developing prints on tape.
5
- Gentian Violet
- Sticky Side Powder
- Titanium Dioxide
- TapeGlo
- Wet Wop
How are fingerprints developed with Gentian Violet?
Reaction with lipids in cell walls
In what type of impressions is Gention Violet used for development?
Latent impressions on adhesive and non-adhesive sides of tape.
What will fingerprints developed with Gentian VIolet look like?
Appear purple
What is Sticky Side Powder?
Commercially marketed suspension formula for developing latent prints on the adhesive side of tape.
For what types of tape does Sticky Side Powder provide excellent results?
7
- Duct tape
- Adhesive bandages
- Paper-backed label
- Masking tape
- Plastic surgical tape
- Clear plastic tape
- Packing tape
Outline the process of developing prints on tape with Sticky Side Powder.
2
- Apply with camel hair brush
- Leave on for 10-15 seconds and rinse with water
How do fingerprints developed with Sticky Side Powder appear?
Black
What is an important thing to keep in mind when using Sticky Side Powder for fingerprint development?
If the solution is left on too long, it becomes difficult to rinse off and the solution may adhere too strongly to some tapes and labels.
Titanium dioxide is useful for developing fingerprints on what surface(s)?
Adhesive side of black electrical tape.
How do fingerprints developed with Titanium Dioxide appear?
White
Outline the process of developing fingerprints with titanium dioxide.
3
- Apply with camel hair brush ad rinse gently with cold water
- Repeat if need/desired
- Allow to dry
What is TapGlo?
Commercially marketed fluorescent dye for developing prints on the adhesive side of tape.
Outline the process of developing fingerprints with TapeGlo.
6
- Pour contents of bottle into clean glass tray
- Place tape exhibit in solution, adhesive side up
- Submerse tape for 10-15 seconds
- Remove tape from tray and gently rinse with water
- Examine tape with ALS
- Pour excess solution from tray back into bottle.
What filter and ALS is required for observing latent prints developed with TapeGlo?
Orange filter
450 nm ALS
What is Wet Wop?
White version of Sticky Side Powder.
On what surfaces is small particle reagent useful for fingerprint development?
Non-porous surfaces, wet surfaces or surfaces that were previously wet
Describe the reaction of small particle reagent for developing fingerprints.
Adheres to oily and fatty components of fingerprint residues.
How is small particle reagent applied to exhibits?
Can be dipped or sprayed
How do fingerprints processed with small particle reagent appear?
Grey
What did scientists discover about developing latent prints from surfaces that had been immersed in aquatic environments?
It is possible to develop prints on these surfaces with CA fuming and basic yellow 40
Outline the experiment that showed CA can be used to develop latent prints on surfaces previously submerged in aquatic environments.
Used glass, aluminum and plastic surfaces
Submerged for 1, 3, 7, 14 days in freshwater or seawater
Were results of CA fuming better on materials submerged in fresh or sea water?
Sea water
List materials that are used for casting plastic fingerprint impressions.
3
Mikrosil
AccuTrans
Dental stone
How is Mikrosil prepared?
Add hardener and mix manually
What is AccuTrans?
Polyvinylsiloxane
How is AccuTrans used?
Mixing tip with dispenser.
What can fingerprints establish?
Presence at a scene
Contact with an item
Differentiate between fingerprint classification vs. fingerprint identification.
Classification = filing and retrieval of fingerprint cards
Identification = Comparison of known prints with unknown prints for the express purpose of identification.
How much area of latent prints can be used for an identification?
~ 10 mm circle of friction ridge skin typically holds enough detail to make an identification.
When was AFIS first introduced?
Late ’70s
What can be done if you want to process balled-up tape for fingerprints?
Freeze the tape and attempt to unravel when frozen
Use solutions used for that purpose
What is the one type of evidence CA fuming could destroy?
Trace evidence like fibers
When should CA fuming cease?
When the test print first starts to appear
Describe how camphor works in developing and preserving fingerprints.
Heat bakes the print in place as well as react with the soot to create a pigmentation that makes the print visible.
