Intro to Forensics

Week 1

Locard’s Exchange Principle

Every Contact Leaves a Trace

States that when two objects come into contact, there is always a transfer of material between them. This principle is foundational in forensic science, emphasizing that criminals will leave behind traces at a crime scene. (Objects can include people or places) Evidence of 2 objects coming into contact.

Alphonse Bertillon

A pioneer in forensic science, known for developing the first system of anthropometry for identifying criminals by measuring physical characteristics. Worked until we realized some people may have the same measurements. 1853-1914

Francis Galton

A key figure in forensic science, known for his work on fingerprint classification and the statistical study of human differences. He established the uniqueness of fingerprints as tools for personal identification. A rough draft of modern fingerprinting. 1822-1911

Edmond Locard

He devolved the world’s first crime lab as well as his exchange principle. 1877-1966

Alfred Lucas

First forensic chemist, 1867-1945

Role of Forensic Science

Applies science to criminal and civil laws that are enforced in a criminal justice system. Provides pieces to a larger investigation. Not about solving crime directly, but helping to add vital contributions. Part of a larger whole.

Data Must be…

Internally consistent for a hypothesis to be valid, Every finding must support the claim. Scientific findings can support or refute possible scenarios – help resolve competing stories about what did or did not happen.

The Science

Is testable, falsifiable, and reproducible
Includes peer review and strives for self-correction

Falsifiable means it is capable of being proven wrong

Pseudoscience/ “junk” science

Has no place in legal settings, can cause false convictions

Evidence

Foundation of forensic science, can be tangible (Objects) or testimonial (Witness statements). Tells a piece of a story, can be used to help determine what happened.

Inculpatory Evidence

Evidence that points to a person being guilty such as a recovered weapon, finger prints, or an admission of guilt.

Exculpatory Evidence

Evidence that proves innocence, such as footage that shows suspect was not there during time crime was commited

3 types of Physical Evidence

Transfer- When someone touches something and leaves for example fingerprints on a weapon (Locard’s Exchange Principle)

Trace- Same as transfer but microscopic (Skin Cells, Hair)

Circumstantial- Facts used to make points/ Additional information (Most common, part of bigger picture)(Fingerprints on gun mean they touched it but did they actually commit the crime with it)

Physical Evidence

You can physically touch it

Direct Evidence

There is no room for misinterpretation, it is a fact and requires no additional work. Ie: Eye witness, photo/video/CCTV footage (If we test powder and it comes back as cocaine it is 100% cocaine)

Inclusive Evidence

Includes a possibility (Has soil in shoes from where crime took place)

Exclusive Evidence

Does not include possibility (Has soil in shoes but not from where crime took place)

Indeterminate Evidence

Does not help/ is not useful to case (Crime was committed in a field and had sand in shoes not soil)

Opinion Evidence

Expert opinion based on data/facts

Testimonial Evidence

What a witness remembers seeing (Not always reliable)

The process of Evidence

Crime Scene

Recovery of Evidence

Examination of Evidence in a Lab

Presentation of Evidence in court

Primary Crime Scene

Where the crime occurred

Secondary Crime Scene

Other Areas evidence was found (Where the body was dumped)

3 Classifications for Crime Scenes

Type of Crime- Homicide, Break and enter

Location- Indoor, Outdoor, Vehicle

Movable Boundaries- Start Large then Narrow down

Warrantless Search

With permission(which can be revoked at anytime)

If people are in danger

If evidence is in danger

Section 8 of the Canadian Charter of Rights and
Freedoms

Right for people to be secure against unreasonable search &
seizure

3 Types of Evidence Interpretation

Deductive

Inductive

Abductive

Deductive

Logical conclusion from facts(Blood sample XX=Female)

Inductive

Using existing data and observations to make predictions (Most serial Killers are men)

Abductive

Gathering what is known and using it to make most likely explanation

Not Match

Similar, Probably, consistent with (Unless a fracture match which is highly unlikely ie. glass shard fitting perfectly into broken window)

Scientific Report must be…

Comprehensive

Easily understood by general public (not just scientists)

Rules of Evidence

Court must admit evidence before it can be used

Only reliable/ relevant information is used(Decided by court, judges, lawyers)

Court makes the rules and has final say

Expert Witness

Expert Opinion

Qualifications

Significance of findings (expert
opinion)

Reasonable scientific certainty

Impartial

Advocate of truth

Must be properly qualified

Admissibility of Evidence

Based on Canadian Evidence Act

Must be directly relevant to case

Probative (Must prove a certain fact that could not be proved without evidence)

Material must deal with evidence at hand

Prejudicial Evidence must be excluded (Past crimes are irrelevant)

General Acceptance Rule

Comes from the case Frye vs U.S. 1923

If technology isn’t commonly used or tested it will not be accepted in court

Qualify an Expert Testimony

Comes from the case Daubert vs Merrell 1993

Evidence/Expert testimony must be relevant to case at hand

Kumho Tire v. Carmichael 1999

Expert does not have to be a scientist

Gate Keeper Rule

The judge can take a more in depth look at the evidence being used

(Generally accepted, Peer review, Method Standard, potential errors, error rates, testability)

R. vs Kahan

What they say out of court can be spoken for them in court (A small child’s parents speaking on their behalf)

Mohan Test

Established in 1994, all expert witnesses must follow 3 basic criteria; necessary, reliable, trustworthy, and truth full

The Opinion Rule

Lay Witnesses can give opinion which is generally accepted when no better evidence is available (Age of sister, Approximate speed of car ect.)

From Crime Scene to Courtroom

Crime Scene —> Recognition & Collection —> Preservation & Documentation —> Laboratory Submission —>Analysis —> Interpretation —> Report —> Court

Chain of Custody

A documented history of the possession, transfer, handling, and analysis of evidence (Examples Of Documents- Video, Pictures, Voice Recording, Notes)

Scene —> Police —> Laboratory —> Analyze —> Evidence Storage —> Court