Unit 1 -
Introduction to
Forensic Sciences
Forensic Science – application of science to court or criminal matters.
Criminalistics = Forensic Science
Dr. Edmond Locard is considered the father of modern-day forensic science.
He was a French criminologist known as the “Sherlock Holmes of France” and established first crime lab in 1910 in France.
Locard’s Exchange Principle states that there is an exchange of materials when two objects come into contact with each other.
This principle is what forensic science is about.
Considered the father of modern day forensic science in the United States
Paul Kirk
1937 – Kirk established the first university-based forensic science program at the University of California at Berkeley.
A forensic scientist is not working for a specific “side” of the law but is looking for the truth.
“When a man who is honestly mistaken hears the truth, he will either cease being mistaken, or cease being honest.”
Thomas Paine (1737 – 1809)
What is truth?
The Webster dictionary defines it as “Conformity to fact or reality; exact accordance with that which is, or has been, or shall be.
A Crime Scene Investigator (CSI) and a Forensic Scientist are not the same thing!
Each have a different function but there is and can be some overlap in function
Crime scene investigators (CSI)
They are usually, but not always police officers trained to collect evidence. (They are not always a scientist)
Collect evidence from and document crime scenes
Under normal circumstances, the job ends when the evidence is delivered to the laboratory
Forensic Scientist
Analyzes the collected evidence when it reaches the laboratory
They must have a degree in science
A forensic scientist rarely visits a crime scene, although it is becoming more common.
Some pieces of evidence may require more than one type of analysis or test be ran.
A scientist must make sure that one test conducted does not destroy or ruin evidence for another test.
Example: A gun with suspect’s fingerprints and blood spots
1. Lift fingerprints
2. Test blood
3. Test fire gun for bullet comparison
Two major duties of a forensic scientist are:
1. Analyze evidence in the lab (and sometimes collect it)
2. Testify in court
May also train other forensic scientists or law enforcement personnel how to record & collect evidence.
Two types of witnesses in court:
Lay Witness:
Testifies only of information perceived through their 5 senses.
May not offer their opinion.
Expert Witness:
Has knowledge or experience about evidence that enables them to reach a conclusion not attainable by the average person.
(Can, by law, only be determined by a judge)
Types of Forensic Sciences:
Pathology
Anthropology
Odontology
Engineering (Physics)
Entomology
Computer
Behavioral/Sociology (Art)
Forensic Pathology
Determine cause and manner of death
Determine when an autopsy is needed
Sign death certificate
Education requirements
A total of 13 – 14 years of post secondary education
Forensic Toxicology
Analyze bodily fluids and tissues to identify the presence of drugs, alcohol, or poisons.
Important is solving cases involving overdose or poisoning.
Forensic Anthropology
Work with skeletal remains
Facial reconstruction
Given the right bones they can determine height, age, gender, and approximately the number of children born to a female.
Skull superimposition
William “Bill” Bass The Body Farm
Forensic Odontology
Odontology = Dentistry
Not typically a full-time job.
Match dental records to remains to help in identification
Postmortem dental records are taken and matched to x-rays taken before death
Match bite marks to those left in substances (Ex. Cheese, plastics) or bruising on a victims’ body.
Engineering and Physics
Helps when something has gone wrong with a mechanical or structural object and in vehicle crashes.
May conduct a failure analysis of structures and why they were faulty.
Determine such things as speed of travel, direction of impact, momentum, who was driving, etc.
A majority of there work comes from accident reconstruction.
Entomology
Blow flies arrive first and lay their eggs in decaying flesh (begins at orifices/wounds)
Other insects my also do this at different times
Depending on temperature and other environmental factors, this happens in fairly consistent time frames.
Squirrel
Entomologists can use this information to give an estimate of the time of death.
Two hours after placement, we already have hundreds of female flies laying eggs
If a person has been poisoned or died of a cocaine overdose, insects will ingest some of the chemicals and a toxicologist can find this in their bodies.
Computer Forensics (Digital Forensics)
Computers are used to both commit and solve crimes
They learn ways to recover data (even from physically destroyed drives), access data that has been encrypted, and sometimes locate evidence and criminals.
This is one of the fastest-growing areas of forensic science
Forensic Chemistry
Analyze chemical substances found at crime scenes, such as drugs, explosives and toxins
May use techniques such as chromatography and mass spectrometry
Behavioral Science (Sociology)
Psychiatrists and psychologists examine defendants – Ex. Insanity plea, competency of an individual to stand trial
Psychiatry is a licensed medical doctor specialty – can prescribe drugs
Psychology is a behavior science and is not a medical doctor
This area is more an art than a science and is not absolute truth.
Can study crime scenes and may look for patterns to help build a profile to help lead investigators to the right suspect.
How to conduct a crime scene investigation
The circumstances encountered at a crime scene will greatly influence what approach is used to process the scene.
The following steps are often used but they can be conducted in a different order, combined or even skipped to meet the needs of the situation.
potential safety and health hazards
2. Plan, communicate, and coordinate
(Crime scene search method)
3. Conduct a primary walkthrough
4. Document and process the scene
5. Record and preserve evidence
CSI personnel may conduct presumptive test at the scene to help identify what evidence is most valuable.
Presumptive tests are useful in determining the type of substance present.
Examples: Ketchup vs blood
Baking soda vs cocaine or other drugs
Presumptive tests help reduce the quantity of evidence sent to the lab
These tests can provide clues to indicate how a crime occurred and who may be involved
Kastle – Meyer Test
Chain of Custody
Chain of custody is a detailed record of who handled the evidence, when, for how long, for what purpose, and the security conditions of storage.
This is to ensure the evidence is the authentic and has not been altered or tampered with
Crime Scene Search Methods
Used to systematically locate and collect evidence. It helps maximize the chances of finding evidence while minimizing the disturbance to the crime scene.
Spiral Method
Useful for scenes where evidence is concentrated in a particular location.
Best for: Small scenes or limited staff
Start outside and move inward
Advantage: Quick for a single investigator
Strip / Line Method
Divides the area into narrow sections.
Allows searchers to move in coordinated, parallel lines. (Usually move forward, shoulder to shoulder and arms length away from the next person).
Best for: Large outdoor areas
Advantage: Simple and systematic
When a suspected piece of evidence is found, they will call over the Team Leader before taking any action.
Move forward together in a straight line to avoid missing any areas.
Grid Method
This can be considered a variation of the strip/line pattern.
It consists of two, line searches at right angles, forming a grid.
Best for: Large areas needing a detailed search.
Advantage: Double coverage ensures no evidence is missed.
Wheel / Ray Method
Features spokes radiating outward from a central point, enabling simultaneous searches across defined sections without cross-contamination
Best for: Circular scenes (Like explosions or body center)
Advantage: Fast, initial coverage
Document in which direction the piece of evidence moved and how far from the center of the explosion it was found.
Zone / Quadrant Method
The scene is divided into zones, each zone is searched separately.
Best for: Rooms, houses, or vehicles
Advantage: Organized an thorough
Link / Point-to-Point Method
There is no set pattern. It requires the investigator to form logical links between the crime scene activity and the likely places additional could be found.
Best for: Complex or indoor crime scenes
Advantage: Flexible, helps build the sequence of events