Forensic Science for Lawyers Concepts of Forensic Chemistry

1. Concepts of Forensic Science for Lawyers
Prof. Prashant Mehta

2. What is Forensic Science
• A special discipline (also called
criminalistics) that is used to discover
the facts about what happened
during a crime.
• It is the study and application of
science to matters of law (criminal
and civil) “science in the service of
law”.
• Includes providing timely, accurate,
and thorough information to all levels
of decision makers in our criminal
justice system.

3. • A criminalist examines physical evidence for legal purposes
• Criminologists study the crime scene for motive, traits, and
behavior as to help interpret the evidence.
– They learn to think like criminals
Criminalists vs Criminologists

4. What happens at a crime scene?
• The first responding officer must secure and protect the
integrity of the crime scene. This is a very important
task! Sometimes crimes cannot be solved and criminals
are set free because the crime scene was not properly
processed.
– Gather information
– Search for evidence
– Document evidence
– Collect evidence
– Preserve evidence so it remains
exactly as it is found at the scene
– Conduct field tests
– Reconstruct the sequence of events

5. The primary crime scene is the location where the crime was committed such as a homicide or a
robbery. A secondary crime scene could be the location where a murder victim was buried, the
victim’s home where evidence of the assailant is found, or a suspect’s home where fibers from the
victim’s clothing or hair were found. In order for a location to become a crime scene, there must be
evidence found at that site.
Primary vs. Secondary Crime Scenes:

6. • Locard's Exchange Principle states that with contact between two
items, there will always be an exchange. This is the basis of trace
evidence collection at a crime scene. “Every contact leaves a trace”

7. Chain of Custody
• The collection, labeling, and testing of evidence. There
must be a documented trail of exactly who has handled the
evidence from crime scene to court. If the chain of custody
is broken because of improper handling or labeling of
evidence, then the evidence may not be admissible in
court.

8. Kendall/Hunt Publishing Company 8
Forensic Area
Collect evidence (non-bodily)
Interrogate witnesses
Arrest criminals
Investigate crime scene
CRIMINALISTICS
(Forensic Laboratory Experts)
LAW ENFORCEMENT
(Homicide detective,
police, FBI, profilers,
others)
MEDICAL EXAMINER
Forensic Chemist / Toxicologist
Questioned Document Examiner
Trace Evidence Specialist
Serologist / DNAAnalyst
Firearms and Toolmarks Examiner
Latent Fingerprint Examiner
Forensic Pathologist
Forensic Entomologist
Deputy Medical
Investigators
Forensic Anthropologist
Photos, sketches, notes
Bloodspatter Analyst

9. • Applies the principles and techniques
of the physical and natural sciences
to the analysis of the many types of
evidence that may be recovered
during a criminal investigation
• May also provide expert court
testimony - Known as an expert
witness - Individual whom the court
determines possesses knowledge
relevant to the trial.
Forensic Scientists

10. Developments in Forensic Science
• 700s AD - Chinese used fingerprints to establish identity of
documents and clay sculptures
• ~1000 - Roman courts determined that bloody palm prints were used
to frame a man in his brother’s murder
• 1149 - King Richard of England introduced the idea of the coroner to
investigate questionable death
• 1200s - A murder in China is solved when flies were attracted to
invisible blood residue on a sword of a man in the community.
• 1776 - Paul Revere identified the body of General Joseph Warren
based on the false teeth he had made for him

11. Developments in Forensic Science
• 1784 - John Toms convicted of murder on basis of torn edge of wad
of paper in pistol matching a piece of paper in his pocket
• 1879 - Alphonse Bertillion developed a system to identify people
using particular body measurements
• 1896 - Edward Henry developed the first classification system for
fingerprint identification
• 1900 - Karl Landsteiner identified human blood groups
• 1904 - Edmond Locard formulated his famous principle, “Every
contact leaves a trace”
• 1984 - Jeffrey’s developed and used the first DNA tests to be applied
to a criminal case

12. People of Historical Significance
• Mathieu Orfila- father of forensic toxicology
• Alphonse Bertillion- devised first scientific system of personal
identification
• Francis Galton- conducted first definitive study of fingerprints and
their classification
• Leone Lattes- developed a procedure to determine blood type
from dried bloodstains
• Calvin Goddard- used a comparison microscope to determine if a
particular gun fired a bullet

13. People of Historical Significance
• Albert Osborn- developed the fundamental principles of
document examination
• Walter McCrone- utilized microscopy to examine evidence
• Hans Gross- wrote treatise on criminal investigation
• Edmond Locard- considered the father of criminalistics;
responsible for Locard’s exchange principle
– States that when a criminal comes in contact with an object
or a person, a cross transfer of evidence occurs

14. Disciplines in Forensics
• Anthropology – examine bones to identify remains and determine other
information such as age, race, and gender
• Art – identify missing children, victims, or suspects through
reconstructive techniques based on age progressions, composite
imagery and knowledge of human anatomy.
• Crime Scene Investigation – gathering information at a crime scene,
collect and preserve evidence
• Criminalistics – collect, identify, and analyze physical evidence from a
crime scene

15. Disciplines in Forensics
• Engineering – determine material or structural failures and reconstruct
events such as accidents or collapse of buildings
• Entomology – study insects found on a decomposing body to
determine time of death
• Jurisprudence – study philosophy of law.
• Medicine (Pathology) – study injuries and disease to determine cause
and manner of death through an autopsy
• Odontology – dentists that identify human remains by matching dental
records, and identify bite marks

16. Disciplines in Forensics
• Psychology & Psychiatry – study human or criminal psychology
and behavior, and profile criminals and victims
• Toxicology – identify and analyze poisons, drugs, and chemicals
and study their effects.

17. Forensic Techniques
DNA Analysis
Use molecular biology to
extract and analyze DNA
from blood, semen, bones,
body tissue, hair roots,
saliva, fecal matter, and any
other material

18. Forensic Techniques
Firearms Examination / Unit
Analyze firearms, discharged bullets, cartridge cases,
shotgun shells, unusual or homemade weapons, and
ammunition components. They determine what kind of
weapon fired a bullet, match bullets to specific weapons,
and determine the trajectory and distance of a shot.

19. Forensic Techniques
Forensic Drug Analysis
Analytical chemistry is used to
identify the presence and quantity
of controlled substances. A drug
chemist analyzes unknown
powders, liquids, plants, pill,
capsules, and other forms of drug

20. Forensic Serology - Identify blood and other body fluids

21. Impression evidence
Study various types of markings on evidence, such as footwear
impressions, tire impressions, and footprints

22. Latent Fingerprints
latent fingerprints are invisible to the human eye. Fingerprints are
detected, developed, and processed in order to compare them to
known fingerprints for identification

23. Questioned Document Examination
scientific examination of handwriting, typewriting, printing, photocopying, or other
mechanical production of written material. Identify ink, paper, or other document
components for authenticity, forgery, or alteration

24. Trace Evidence
examine hair, fibers, glass, soil, plants, minerals, and many other
different types of materials. Substances are studied under a
microscope and chemical techniques can be used to identify and
individualize evidence even when found in very small quantities

25. Voice Analysis
ties unknown voices in recorded messages to particular speakers
based on speech patterns that are unique to every individual

26. Photographic Unit
• Applies specialized photographic techniques for recording and
examining physical evidence

27. All About
Evidence

28. • Is any item or information gathered at the
scene of a crime, or at related locations
which tends to disapprove or establish
something.
• Any tangible material that can be used to
prove the facts of a matter in a court of law.
• Expert witness: someone who testifies in
court as a qualified expert in a particular
subject area
 It can be divided into two general goods:
• Testimonial Evidence
• Physical Evidence
Evidence

29. Physical Evidence
• Tangible tend to prove or disapprove a fact
• Real evidence
• Refers to any item that would be present at the crime
scene on the victims out found in a suspects possession.
• more reliable than testimonial evidence
• Can be any material or object in any shape, size, form.

30. Physical Evidence
• Types of Physical Evidence:
• Trace Evidence
• Transient Evidence
• Conditional Evidence
• Indirect Evidence
• Individual Evidence
• Class Evidence

31. Trace Evidence
 refers to physical evidence that is found in small but
measurable amounts. (For example: hair, fibers, skin cells,
DNA, blood, etc.)

32. Transient Evidence
 temporary evidence can be easily changed or lost.
Recorded at the time by usually the first office at the
scene. (For example: odors, temperature, imprints, etc)

33. Conditional Evidence
 produced by a specific action or event at
the scene. (For example: lights, doors,
windows, position of furniture, etc)

34. Indirect Evidence
 does not prove or disprove a fact in question. (For
example driving under the influence)
+

35. Individual Evidence
 can be related to a single source. (For example
fingerprints. Handwritings, etc)

36. Class Evidence
 Can be associated with a group of items that
share properties or characteristics. (For
example: blue jeans)

37. Arson Evidence

38. Physical Evidence

39. Chemistry
The study of composition, structure, properties, and reactions of a
substance which help us identify a suspect. Identify and analyze toxic
substances, fire accelerants, gunpowder residue, explosives and other
chemical substances.

40. Biology
The study of the investigation of
living matter, or once living
matter, in reference to its origin,
behaviour, and classification.
Applies the knowledge of biological
sciences in order to investigate blood
samples, body fluids, hair, and fiber
samples.

41. Physics
The study that comprises of all investigations that deal with
motion, force, and dynamics. Incorporates the principles of
chemistry, physics, and geology to identify and compare physical
evidence.

42. Other Crime Lab Services
• Toxicology Unit- examines body fluids and organs for the
presence of drugs and poisons
• Latent Fingerprint Unit- processes and examines evidence for
latent fingerprints
• Polygraph Unit- conducts polygraph or lie detector tests
• Voiceprint Analysis Unit- attempts to tie a recorded voice to a
particular suspect
• Evidence Collection Unit- dispatches specially trained personnel
to the crime scene to collect and preserve physical evidence

43. Other Forensic Science Services
• Forensic Pathology- concentrate closely on the understanding of
types and causation of injuries and causes of sudden and
unnatural death
– Deals with the different stages of death
• Rigor mortis- stiffening of the body (occurs within first 24 hours)
• Livor mortis- settling of blood closest to the ground (occurs up to 12 hours)
• Algor mortis- results in loss of heat

44. Other Forensic Science Services
• Forensic Anthropology-concentrates on the identification of
deceased individuals whose remains are decomposed, burned,
mutilated or otherwise unrecognizable
• Forensic Entomology- is the study of insects and their relation to
a criminal investigation, commonly used to establish the time of
death
• Forensic Psychiatry- work with courts in evaluating an individual's
competency to stand trial, defenses based on mental diseases or
defects (e.g., the "insanity" defense), and sentencing
recommendations

45. Other Forensic Science Services
• Forensic Odontology- evaluates teeth to determine the
identification of the deceased
• Forensic Engineering- investigation of materials, products,
structures or components that fail or do not operate/function as
intended, causing personal injury for example
• Cyber technology- involves the examination of digital evidence

46. Listening
Attention
Patience
Questions