Fingerprint patterns

Fingerprints are unique

• Composed of friction ridges which give us better gripping ability (tire treads)

• Bifurcation – a single friction ridge that has split into two

• Ridge ending – the point where a friction ridge ends

• Short ridge – a single friction ridge that runs only a short distance

• Dot (island) – a friction ridge that is about as long as it is wide

• Enclosure – a single ridge that splits in two and then comes back together to form a single ridge again

• Spur – a bifurcation in which one of the ridges ends after a short distance

• Crossing – two ridges that cross over one another and form an X

• Crossover – a short ridge that runs between two parallel ridges

Fingerprint ridge characteristics

• Minutiae- ridge characteristics that make fingerprints unique                                          

Remember…

• Most important minutiae (characteristics) are bifurcations and ridge endings

• Identical twins have different fingerprints

Fingerprints do not change over a person’s lifetime

• Friction ridge pattern determined in the womb by the dermal papillae

• Bank robber John Dillinger tried to remove his fingerprints by using a corrosive acid and had plastic surgery performed on his face to conceal his identity– Shot and killed on July 22, 1934 during the

famous “lady in red” incident– Even with scar tissue, FBI was able to match

Types of Fingerprints

• Visible prints (can be easily seen)– Made in oil, grease, blood

• Plastic prints– Made in soft material

• Latent prints (invisible to human eye)– Require treatment to make the oils and salts

produced by the sweat glands visible

Visualizing latent fingerprints

• Physical methods– Lasers

• Chemicals produced by the skin• Exposed to UV light• Reemit the light in the visible range• Must wear goggles• Advantage: large area at once• Disadvantage: not as sensitive as other methods

– Dusting powders• Oils left behind are sticky• Very fine particles adhere to surfaces• Black powders suited for light surfaces• White powders suited for dark surfaces• Application by brush• Some powders are fluorescent and glow in the

dark• Works best on hard, nonporous surfaces

• Chemical methods– Superglue fuming

• Chemical comes into contact with oils and polymerizes into a hard, white substance

– Iodine sublimation (directly from solid to gas)• Iodine vapor coats the unsaturated oils• Produces a golden-brown image• Will quickly fade unless sprayed with a starch solution

– Ninhydrin• Sprayed from aerosol can• Then put in an oven, left to develop

– Silver nitrate

Recording and lifting of fingerprints

• Should be photographed as soon as they are visualized

• Entire object can be sent to lab

• Print can be lifted using adhesive tape

FBI Classification SystemLoop

Plain Whorl

Double Loop

Arch

Central Pocket Whorl

Tented Arch

FBI System

Primary Classification

R. Index R.Ring L.Thumb L.Middle L. LittleR. Thumb R. Middle R. Little L.Index L.Ring16 8 4 2 1The presence or absence of whorl pattern determines classificationIf whorl is present-assign the numbers aboveIf loop or arch is present-assign a zeroThen add a 1 to both the numerator and denominator-the fraction obtained

is the primary classification

Example

If the right index and right middle fingers are shorls and all of the others are loops, then the primary classification is:

16 + 0 + 0 + 0 + 0 + 1 = 17

0 + 8 + 0 + 0 + 0 + 1 8

Deltas & Cores

bsapp.com

Integrated Automated Fingerprint Identification System

• Arrested offender’s prints sent to FBI for identification

• The card method took 2 weeks to process• In the 1970s the FBI, British Home Office,

and the Japanese National Police Agency developed a computerized method of scanning fp images into a computer and creating software to digitize the minutiae. (AFIS)

• Standard was created• New system IAFIS (1999) not based on 10

finger system• Functions of IAFIS lab:

– Enhance image– Comparison of prints– Search of latent fingerprints when there is no

suspect– Search of new arrest records against an

unsolved latent print– Creation of special files for major criminal

investigations– Victim identification

The one that got away….again and again

• Jan. 2004 Jeremy Bryan Jones arrested in GA for trespassing

• Gave the police an alias of John Paul Chapman• Arrest warrant was out for him under his true name

(rape, sodomy, and jumping bond)• Fingerprinted, but IAFIS did not correctly match• Arrested and freed 3 times!• He was responsible for the murder of 13 women• http://www.amw.com/fugitives/brief.cfm?id=28661