Pre-Trial ProceduresThe Criminal Investigation

Expectations •CL2.01 explain processes of police

investigation

•CL2.02 explain pre-trial procedures, including processing evidence

Objectives•Create and classify your own fingerprint

•Dust for fingerprints, classify, analyze and match them to our classroom database.

The Crime Scene•Police have the right to cordon off the

crime scene to make sure no evidence is lost or tampered with.

•Police can refuse entry to a crime scene. •HOWEVER, if the incident involves a

death, the coroner has jurisdiction over the area.

The Crime Scene Continued •The area will be photographed and

searched for items such as hair or fibre samples, blood, forced entry, physical struggle, fingerprints, footprints, or weapons▫This is called forensic evidence.

•Police will also question witnesses about their knowledge of the crime or the persons involved.

Processing Physical Evidence: Fingerprints

•Forensic scientists analyze the information collected.

•Fingerprints are compared with those on

file at the RCMP central repository in Ottawa.

•The patterns of ridges on our finger pads are unique: no two individuals—even identical twins—have fingerprints that are exactly alike.

Like a snowflake!

•Injuries such as burns or scrapes will not change the ridge structure: when new skin grows in, the same pattern will come back.

•Dactyloscopy ▫ the practice of using fingerprints to

identify someone.

•Mistakes can be made in fingerprint identification▫usually only a portion of a print is available

and can be distorted and hard to read, especially in a messy crime scene situation (i.e., BLOOD!)

•It is extremely important that specialists are able to properly dust and lift fingerprints at a crime scene to be able to classify and match them to those in the database.

How are fingerprints classified?

Are we able to classify our own fingerprints in class?

YES!

Classifying FingerprintsAll fingerprints can be identified as one of

three types: Arches, Loops, Whorls

1. Arches: forming ridges that run from one side of the print to the other and curve up the middle

2. Loops: showing stronger curves than arches with ends that start on one side of the finger, loop around and end up in the same place

▫ Don’t get these confused with full circles or ovals.

3. Whorls: forming complete ovals, often in a spiral pattern around a central point.

Your turn!Directions:

• Print your name on the lined side of one of your cue cards – set it aside

• Take two pieces of scotch tape and tape them together to create a ‘thicker’ piece of tape▫ (sorry guys, the dollar store only had skinny tape)▫ Set the tape aside (on the end of your desk)

• Rub the second cue card roughly with your pencil• Press your index finger on the pencil-lead dust• Place the sticky side of a piece of tape on the dusted finger• Take the tape with the fingerprint and tape it on your first

cue card on the blank side – not the side with your name on it

• On the lined side (with your name) Label the fingerprint to identify which finger you have printed (i.e., Index or I) and classify your print using the fingerprint handout

Dusting for Fingerprints•It is extremely important that specialists

are able to properly dust and lift fingerprints at a crime scene to be able to classify and match them to those in the database.

•Dusting is a method that is used to lift

prints from hard surfaces

•Chemicals are needed to lift prints off smooth surfaces

Directions: Dusting for fingerprints• 1. Press your index finger in the play-doe. • 2. Press your index finger on the glass • 3. Coat the fingerprint with a dusting of baby

powder. • 4. Lightly press the powder with the brush – but

don’t brush off the powder! • 5. Bang the glass on the desk to get the excess

powder off the glass. • 6. Place the sticky side of the tape on the dusted

fingerprint. • 7. Lift off the tape and place it on the black

construction paper.• 8. Print your name on the back side of the print.

Activity: •In groups of 4, you will go to each station

and try to match the dusted print with the databank prints.

•On your cue card (you will get a new one from me) you will write your answers down.▫Example: A4, G7, J12 ▫ONE cue card with answers per group is

sufficient•Write your group member names on the cue

card. The team with the most correct responses wins!

The Crime Scene Continued •There are strict procedures on the seizure,

handling, and storage of evidence: 1. no evidence is left unattended; 2. the case officer must secure evidence in the

police property locker; 3. transferring evidence is the responsibility of the

case officer; 4. no evidence can be removed from property

locker without appropriate authority and signature. This is to maintain the chain of custody of the evidence.

Processing Physical Evidence

Trace Elements, Blood, DNA

Trace Elements• Dirt, dust, residue

• Provides link between suspect and the crime

• Example: wood or other materials at an arson scene may produce trace elements of the accelerant used to start a fir.▫During an investigation into a series of fires in

Hamilton, experts linked the fluid used to start fires to fluid found in the garage of one of the suspects. Both samples were mixed in exactly the same proportions and were not sold by any other manufacturer.

•The transfer of hair and fibres ▫Typically analyzed in homicides, kidnapping and

aggravated assault•Hair and fibres are trace elements because they

can be found either on the victim or the accused.

•Hair may not reveal specific people (like fingerprints), but they can reveal racial background, area of the body the hair came from and the persons blood type.

Animal fur is more scaly than human hair

Hair samples with the root can provide the most information – DNA us usually present.

Various Fibre SamplesFibers from the crime scene can be traced to criminals

(Example: Carpet fibres from the crime scene found on the suspects shoe)

Blood•Blood samples are important in impaired

driving cases or crimes committed when under the influence ▫Percentage of alcohol or substance levels

can be important in cases where mens rea is an issue.

•Blood Spatter Analysis▫study of the size and shapes of the drops on

the floor can determine from the height at which they fell

▫Shape of drop can indicate movement▫Blood spatter on the wall can determine

force and direction of the blow.

▫Blood Spatter News Report

DNA•All human beings have a distinctive

genetic code within their chromosomes which are composed of DNA▫Deoxyribonucleic acid (DNA)

•Lab analysis of blood stains, semen, saliva, vaginal secretion, skin and hair follicles can lead to the identification of an individual through his or her distinctive genetic code.

CSI: Crime Scene Investigation

Season 10, Episode 5“Bloodsport”