Module 1 Types of Evidence & Fingerprint Analysis

Question 1

Types of physical evidence

Answer 1

Identified and Individualized

Fingerprints

Hair

Blood

Bullet casings

Paint fragments

Fibers

Question 2

Individualized physical evidence

Answer 2

Unique can be directly linked to specific person or source Finger prints , DNA , bullet casings, dental impressions

Question 3

Identified physical evidence

Answer 3

Common source into crossing items having some more properties Clothing, shoe print, blood type Useful in 2 ways When directly supports individualized evidence And/or When presented with additional pieces of identified evidence

Question 4

Finding an interpreting physical evidence from a crime scene is crucial because it can?

Answer 4

Prove a crime has been committed

Establish identity of the suspect(s)

Exonerate the innocent

Corroborate the victims testimony

Lead to a confession from suspect

More reliable than eyewitness

Expected by Judge/ juries

Question 5

What are the 3 types of finger prints

Answer 5

Visible

Latent

Physical

Question 6

What is a Visible Print ?

Answer 6

Easily seen by human eye

May be left on an object at crime scene b/c of Blood Perspiration Dirt/oils on hands

Question 7

Latent

Answer 7

Hidden or concealed in some way Not visible to naked eye Most are composed of perspiration and/or body oils

Latent fingerprints are those that are not apparent to the eye but can be made sufficiently visible, as by dusting or fuming, for use in identification

Question 8

Physical

Answer 8

When distinct impression is left upon soft materials such as… Wax Food items Caulking around window/doors

Question 9

What are the 2 layers of the skin where prints are?

Answer 9

Skin is made up of 2 layers The outer layer EPIDERMIS Inner layer DERMIS Burns or abrasions cuts don’t alter ridge pattern If a cut is deep enuf it can damage the dermis causing a scar

Question 10

Epidermis

Answer 10

Where fingerprint ridges are found

Question 11

Dermis

Answer 11

contains sweat glands

Question 12

3 main types of ridge patterns are?

Answer 12

Arches

Loops

Whorls

Question 13

Arch sub-classifications

Answer 13

Plain/simple arch Tented arch

Question 14

Loop sub-classifications

Answer 14

Ulnar loop Radial loop Double/twinned loop

Question 15

Whorl sub-classifications

Answer 15

Plain whorl

Central pocket whorl

Accidental whorl

Question 16

what % of the population has each type of print

Answer 16

Arches 6% of people (rarest)

Whorls 34% of people

Loops 60% of people

Question 17

How is a fingerprint match made ?

Answer 17

print identification isn’t determined solely by its pattern,

but also by careful analysis of points within the pattern called ridge characteristics or minutiae.

average print has more than 100 unique ridge characteristics or minutiae.

Identification of 8-16 ridge characteristics within a print is used to match a print to a suspect.

Question 18

What is lifting powder \use of this powder

Answer 18

Lifting powders are made of one type of metal, or homogeneous mixtures of metals.

Lifting powder application is useful to enhance fingerprints that have been left upon hard surfaces. They work best upon smooth, solid surfaces

Question 19

What safety precautions should be used when working with lifting powder?

Answer 19

Inhalation of metal lifting powders can be harmful to the tissue of the lungs;

Protective goggles and mask should be worn.

Question 20

How are prints lifted when using lifting powder ?

Answer 20

After lifting powder has been applied, a fingerprint is ‘lifted’ using a wide piece of clear smooth tape.

Afterwards, the print is analyzed by forensic experts.

Question 21

How do Forensic experts choose lifting powders ?

Answer 21

Individual preference

Availability

Cost

Question 22

What are lifting powders applyed with ?

Answer 22

In the early days of crime scene investigation, lifting powders were gently applied using feathers.

Today, specialized brushes that contain very soft bristles such as bird feathers, squirrel hair, camel hair, or fibreglass are used

Another type of lifting powder brush has a strong magnet at the end to attract the metal-based lifting powder not sticking to the surface as it is applied.

Question 23

How dose lifting powder work ?

Answer 23

The scientific principle of lifting powders is that the positively-charged metal powder is attracted to the predominately negatively-charged body oil residue in sweat that is found in a fingertip impression. The powder is highly attracted to the oily, negatively-charged fingerprint residue but not to the surrounding surfaces.

Question 24

What is Iodine Fumigation ?

Answer 24

The related reaction is iodine fumigation enhances fingerprints

that have been left upon light-coloured, light weight, and low density objects such as paper, some types of fabrics such as light-weight cottons and some polyesters.

simple technique, a small amount of iodine is placed in the bottom of a glass chamber

object bearing the suspected latent prints is suspended from the top of the chamber.

chamber is then sealed,

and the above reaction occurs if sodium chloride (sweat) is present.

After a reaction occurs, the prints are then exposed to a fixing solution (a mixture of cyclohexane and dichloromethane) that causes the prints to turn dark-blue.

The prints now become permanent.

If a fixing solution is not applied, the exposed fingerprints begin to degrade after the object has been removed from the glass chamber.

where results are often ready within a few minutes,

Question 25

Reaction and reasoning behind Iodine Fumigation

Answer 25

sweat contains sodium chloride - NaCl - an ionic compound composed of a single sodium cation (Na+) attracted to a single chloride anion (Cl-). Sodium chloride is a salt - hence the reason sweat tastes salty. Within fingerprint residue, and especially within sweat, many sodium cations occur (Na+).

All negatively-charged anions are highly attracted to positively-charged cations. Iodine in its pure state is a non-metal solid that produces negatively-charged anions (I-). So when iodine is exposed to the sodium chloride in sweat, a single replacement reaction occurs in which the iodine displaces the chloride ions and attaches to the sodium ions to produce sodium iodide (NaI).

Question 26

Cyanoacrylate Fumigation

Answer 26

Cyanoacrylate(main component of a strong glue) enhances latent fingerprints

when Cyanoacrylate reacts with the body oil residue in a fingerprint, it produces a visible whitish-grey film that is especially noticeable on dark-coloured objects.

Answer 27

prints that have been left upon solid objects that are smooth surface or slightly textured surface such as metals ,knife ,handles, guns, bullet cartridges, pop cans) hard plastics such as credit cards, knife handles, guns)

visible prints from cyanoacrylate fumigation can take from one to 24 hours or more.

After a reaction does occur, the object is removed and is analyzed and/or photographed. An advantage to prints enhanced by cyanoacrylate is that they do not degrade. They are permanent records.This type of print cannot be lifted, so it must be photographed for analysis.

small amount of cyanoacrylate is placed in the bottom of a closed chamber

.The object bearing the latent prints is suspended in the top of the chamber.

The chamber is then sealed,

and heat and moisture are introduced (For example, a light bulb or warming plate and a cup of water are adequate)

Over time, a reaction occurs causing the cyanoacrylate to change from a liquid to a gas (sublimation). It is attracted to any body oil residue present in the chamber.

Answer 28

Short-term vs. Long-term Latent Fingerprint Samples

Fingerprint impressions can remain in place for a surprisingly long time. Even exposure to the elements such as heat, cold, and moisture very often will not destroy a fingerprint impression. However, a smudged fingerprint impression is typically of little value to forensic experts. Smudging occurs if pressure has been placed upon the fingerprint impression or when the subject’s finger slides across a surfac

Question 29

Experiment 1 Solutions

Question 30

Experiment 2 Solutions

Question 32

What kind of print is this ?

Answer 32

Question 33

What type of print is this ?

Answer 33

Question 34

Answer 34

What type of print is this?

Question 35

What print is this?

Answer 35

Question 36

What is this print?

Answer 36