Forensic Science Lesson 07: Fingerprints Part 2

Fingerprinting Part 2

Multiple Choice

When are fingerprints formed

• Shortly After Birth

• At Two Years of Age

• At 10 Weeks Gestation

• At 17 Weeks Gestation

• At 5 Weeks Gestation

Multiple Choice

True or False: Fingerprints are considered to be class evidence.

• True

• False

Multiple Choice

What is the least common type of fingerprint?

• Loop

• Whorl

• Arch

Multiple Choice

True or False: Fingers are the only part of the body that have ridges on them

• True

• False

Multiple Choice

How many deltas do arch fingerprints have?

• 0

• 1

• 2

• 3 or more

Multiple Choice

True or False: Other animals have fingerprints as an evolutionary advantage

• True

• False

Multiple Choice

The small triangular region found on some fingerprints is known as a

• spur

• eye

• bridge

• delta

Case Study: John Dillinger

• Notorious gangster during the great depression

  • Declared Public Enemy Number 1 in 1934

• Wanted to disguise his fingerprints

• Learned that the acid from pineapple plants could destroy fingerprints from farm workers

  • Paid a doctor to live with him and regularly destroy his prints with acid

    • Left scars behind that could be used to identify him

• After his death, his fingerprints were taken and connected to several different crimes

Changing Fingerprints

• It is not possible to permanently destroy fingerprints, because your skin will grow back

• Prints can be temporarily damaged by two methods

  • burning with heat

  • dissolving with acid

• Certain jobs involve working with chemicals that can damage fingerprints

How Reliable are Fingerprints?

• Computers can only do so much in terms of recognizing fingerprints, so there is a lot of room for human error

  • If a person mismarks a minutiae pattern, the wrong person can be identified

  • If a person does not look at enough minutiae, they could get multiple matches

• Results are often checked and double checked to make sure the correct suspect is identified

Case Study: The Madrid Train Bombings

• March 11, 2004: 10 Bombs explode on four different trains in Madrid Spain killing 193 people

  • detonated remotely, so only remains from the bombs could be used to identify the perpetrator

• Fingerprints found were incorrectly matched by the FBI to Brandon Mayfield an American who had not left the country for several years

  • Was held for two weeks as a prime suspect until Spanish authorities proved a mistake was made

Analyzing Fingerprints

• In the past, the analysis of fingerprints could take a long time to complete

• 1999: The Integrated Automated Fingerprint Identification System was created

  • A digital database that can automatically compare different prints to find a set of close matches that a human can review

    • Allows for quick results ( around 2 hours is good)

Multiple Choice

Is it possible to completely change your fingerprints?

• Yes

• No

Multiple Choice

Can a computer 100% identify a suspect based on fingerprint analysis

• Yes

• No

Types of Fingerprints

• When Fingerprints are collected, they are categorized by how they were left behind

  • Can give an idea of what happened

• Patent Fingerprints: Visible prints left behind by any liquid on the hands

  • blood, ink, water, oil

• Plastic Fingerprints: Indentations left in a soft substance

  • Clay, putty, caulk

• Latent Fingerprints: hidden prints left behind from skin secretions and dust

  • Can be revealed using dust or chemical reaction

Collecting Latent Fingerprints on Smooth Surfaces

• Normally, Latent fingerprints are not visible

• Depending on the object being tested, different tests can be used

  • Usually, some form of dusting is done on hard smooth surfaces

    • Carbon Dust is sprinkled on the prints to make them more visible

    • Tape is then applied to collect the dust imprint and placed on an evidence card

Collecting Latent Fingerprints on Non-Smooth Surfaces

• For fingerprints on objects that are not hard or smooth, different chemicals can react with the prints and make them more visible

  • Ninhydrin & Cyanoacrylate react with amino acids in sweat

  • Silver Nitrate reacts with salt left behind in sweat

  • Iodine binds to carbohydrates

Multiple Choice

Fingerprints that are actual indentations left in some soft material such as clay or putty are referred to as

• plastic fingerprints

• patent fingerprints

• latent fingerprints

• indented fingerprints

Multiple Select

A burglar pushes their hand up against some wet paint, leaving an impression behind. Which type of print(s) could this be considered?

• Patent

• Plastic

• Latent

• indented fingerprints

Multiple Choice

Every time you touch your phone screen, you leave hard-to-see marks behind. Which type of print(s) could this be considered?

• Patent

• Latent

• Plastic

• indented fingerprints

Multiple Choice

You are holding a chocolate bar on a hot day, and it starts to melt in your hand. Which type(s) of fingerprints would be left on the candy?

• Patent

• Latent

• Plastic

Multiple Choice

The use of fingerprints in identification is not perfect because

• The current technology depends on humans to input and analyze the information, and humans make mistakes

• Many people have the same exact fingerprints

• People can easily change their fingerprints

• All of the given answers are correct

Fingerprint Evidence in the Future

• As digital technology improves, we can collect more detail on prints

  • Some scanners can show how pores in the skin rest on fingerprints, making them even more unique to each person

• Scanners can hook up to databases to compare prints at the time of arrest to cold cases