Forensics Ch. 7/8

What are the four latent print categories?

-Latent Print

-Patent

-Impressed/Plastic Print

-Etched Print

Define: Latent Print

The reproduction of the friction ridge of the finger in perspiration or oily matter on an object to be touched (can not see it)

Define: Patent Print

A fingerprint that is visible to the naked eye

Define: Impressed/Plastic Print

Fingerprint that is impressed into soft pliable substance  (copper, brass; coatings keep the fingerprint there forever bc of oxidization)

Define: Etched Print

Fingerprint that is imbedded into a metal surface

Latent Prints are made of ___?

• Salt (sweat)

• Amino Acids

• Water

• Oils (typically see)

What can latent prints be left in?

• Blood

• Fats/Oils (fast food)

• Dirt/Grease (mechanics)

• Dust

Are dust prints a takeaway or deposition? What is an example?

• Takeaway

• Break and entering, dust above a window sill; you can not process these prints)

What three factors affect latent prints?

• Pre-Transfer Conditions

• Surface Types

• Environmental Conditions

Describe pre-transfer conditions when it comes to effects on latent prints.

What substances are on the ridge, pressure applied, movement upon contact, gloves worn, donor, etc.

Explain why or how surface types can affect latent prints.

Surface touched may have not been conducive for latent prints (Rubber stamp; rough vs smooth; easier to pull from smooth

Explain environmental conditions and its effects on latent prints.

What happens after deposition of the latent (weather, cleansing, surface, evaporation, etc.) time sensitive to pull prints

Are we able to determine the age of latent prints? Is there any way to determine them?

Unable to determine by examining latent only. Could possibly use additional information to determine using history or age.

Give some examples of what smooth surfaces latent prints can be on. How successful are they?

• Glass (most successful)

• Plastic

• Finished/Painted Wood

• Metals

• Firearms/Knives

• Baggies (drug baggies)

• Aluminum

What rough surfaces are latent prints left on? How successful are they?

• Unfinished wood

• Cloth

• Paper (not so successful because your oils will be absorbed)

• Rubber

• Rock (successful)

• Etched glass/brass

• Leather/Vinyl

• Tape (most successful)

What do we need to process at a scene?

• Any possible P.O.E (point of entry)

• Areas of blood swipes

• Dust Prints

• Walls, Door Jams

What two categories are there for latent print processing?

• Fingerprint powder

• Fingerprint Chemicals (rough surfaces)

What does POE stand for? Give an example.

• Point of Entry

• E.g., Window

Latent print enhancement improves contrast by using what?

• Alternate light source (Forensic light source)

• Photograph

• Adobe Photoshop

If using alternate light source, what two prints do you need for it?

• Naturally luminescent print

• Semi-Visible Latent

If you were to view with an alternate light source, what can you use?

• Super glue fuming and basic yellow dye stain

• Raye Dye-Stain

• DFO- Fluorescent Paper Process

• Red Fluorescent Powder

What are things from a scene that need to be photographed?

• Dust print

• Patent prints (ziploc baggie w/ white substances)

• Footprint in paint

What are four ways for chemical processing?

• Ninhydrin Development

• Amino Black development (blood)

• Small Particle Reagent (SPR)

• Wet WOP (sticky side of tape)

Define: Ninhydrin Development

• Must photograph or scan (paper fingerprint will be gone within a month)

• Timely process

• Expensive equipment 

• Need controlled environment and ventilation

Define: Amino Black Development

• Used for blood and it is a chemical dye stain that dyes proteins bc it sticks to them

Define: Small Particle Reagent (SPR)

• Wet surfaces 

• This is a powder with a detergent that you can spray; it will adhere to the print 

Define: Wet Wop

• Pre-mixed solution of detergent and black (or white) conventional powder

• Used (painted) on the ticky side 

• Superglue due stain may be used on non-sticky side

• Place pieces of tape on frosted transparency sheet once processed

What supplies needed for powder processing?

• Zephyr Brush

• Magnetic Powder Applicator/Want

• Black Powder (goes w/ zephyr brush)

• Black Magnetic powder (mag wand)

• Frosted/Clear lifting tape

• Latent Lift card

What steps are needed to be taken for powder processing?

• Visual check (sometimes u dont need to powder)

• Process with powder

• Remove Excess powder

• Lift with tape

• Label lift card

• Photograph

How do you use a latent lift card?

• One latent lift per card

• Each card is a separate piece of evidence 

• Describe location

What is one important conclusion from lifting prints?

Technique based, the more you do it the better you will become