Fingerprints Types and Techniques

Fingerprints

Types and Techniques

Many people recognise finger prints and marks as CSI evidence, be it from

The News

TV

Movies

but how much do you know other thank the surface level?

other than

surface level

The palms of our hands and soles of our feet are covered in ridges

However, what they leave behind are fingerprints.!

marks!

prints!

The patterns that these ridges form are unique and are our fingerprints!

Prints are first separated by the PATTERN OF RIDGES

LOOPS

COMPOSITE

ARCHES

WHORLS

And then are identified further using RIDGE CHARACTERISTICS

BIFURCATION

EYE

ENDING

ENCLOSURE

HOOK

Marks can be separated too!

Visible marks are formed when blood, paint, etc. transfers from a finger/thumb to a surface!

Plastic marks are three dimensional and are left in soft surfaces such as wax and wet paint!

VISIBLE PLASTIC LATENT

Latent marks are invisible, require enhancement! They are made of natural secretions and contaminates (drugs, makeup, etc).

Click here to edit this text

These marks can be affected by

The surface type

Time

Storage

Environment

Mark composition

SURFACE TYPES

porous non-porous smooth non-porous rough

• Liquids sit on top
• Cause fragile marks

• Liquids sink in

• Paper
• Cardboard
• Untreated wood

• Varnished
• Painted
• Plastics
• Glass

• Vinyl
• Leather
• Textured surfaces

The surface type is important in deciding which methods should be used!

Wet marks use PHYSICAL DEVELOPER – A silver based reagent that turns impressions DARK GREY or BLACK

For porous surfaces it depends whether the mark is

DARK

GREY

BLACK

DRY

WET

Dry marks use NINHYDRIN – it reacts with amino acids to form visible prints on an ORANGE to PURPLE scale!

ORANGE

PURPLE

The vapours polymerise (join together!) on the latent marks.

Superglue fuming places the marks in a heated chamber with superglue and water.

Non porous surfaces can use

Powder suspension

Iodine fuming

The marks then show as a white residue!

This method is good for large items e.g. bikes

Powdering

Superglue fuming

Metal Flake Powders

Magnetic Powders

• Aluminium, Brass
• Extremely sensitive due to flat flake shape
• Most effective on glass!

• City Red, City Black, Magenta Flake
• Useful on rough surfaces!
• Uses a magnetic wand

Powdering

Flourescent Powders

Granular Powders

• Squirrel brush (animal hair!)
• Variety of colours - pink, green, yellow!
• Used with UV light!
• Good for multicoloured surfaces!

• Less sensitive

• Black and white colours!

Want to learn more?:

Fingerprints: Analysis and Understanding the Science By Mark R. Hawthorne, Sharon L. Plotkin, Bracey-Ann Douglas www.forensicsciencesimplified.org/prints/how.html www.crimemuseum.org/crime-library/forensic-investigation /fingerprints/ https://www.bvda.com/en/latent-fingerprints

Tiny scientists illustrated by: @goblinmutt.art on instagram!

Royalty Free Music: www.bensound.com