Chapter 1
Forensic Science and Observation
© 2021 Cengage Learning, Inc.
Introduction
• “Forensic” derives from the Latin word
forensis, which means “of the forum”
• The ancient Roman forum was where scholars
debated issues and solved crimes
• However, debating is not forensic science
• It is about the skill of observation to uncover
evidence and discover the facts of a crime
© 2021 Cengage Learning, Inc.
What Is Forensic Science?
LO1: Describe the purpose of forensic science.
(1 of 2)
• Forensic science
– Using science to help resolve legal matters
• Forensic investigator
– Collects and examines physical evidence
– Reports to law enforcement
– Possibly testifies in court
© 2021 Cengage Learning, Inc.
What Is Forensic Science?
LO1: Describe the purpose of forensic science.
• Tools of the forensic investigator
– Ability to observe, interpret, and
report findings
– Ability to identify the evidence,
document it, and determine its
significance
© 2021 Cengage Learning, Inc.
What Do Forensic Scientists Do?
LO2: Explain the role and responsibilities of a forensic scientist.
(1 of 4)
• Observation and application
– Find evidence
– Collect data
• Qualitative data
• Quantitative data
– Analyze data
© 2021 Cengage Learning, Inc.
What Do Forensic Scientists Do?
LO2: Explain the role and responsibilities of a forensic scientist.
(2 of 4)
• Communication
– Convince a jury that evidence is:
•
•
•
•
Scientific
Reliable
Valid
Sufficient
© 2021 Cengage Learning, Inc.
What Do Forensic Scientists Do?
LO2: Explain the role and responsibilities of a forensic scientist.
(3 of 4)
• Deductive reasoning
– Scientific method
•
•
•
•
•
•
State the problem or question
Propose a hypothesis
Conduct an experiment
Collect data
Analyze data
Draw a conclusion
© 2021 Cengage Learning, Inc.
What Do Forensic Scientists Do?
LO2: Explain the role and responsibilities of a forensic scientist.
(4 of 4)
• Deductive reasoning
– Claim Evidence Reasoning Model
•
•
•
•
•
Make observations
Determine what question you want to answer
Make a claim and an assertion
Provide evidence
Provide reasoning or justification
© 2021 Cengage Learning, Inc.
Observation and Perception
LO3: Distinguish between observation and perception.
(1 of 2)
• Observation
– Gathering information through senses
• Sight, taste, hearing, smell, touch
– Done largely without thinking
• Our brains select what information to take in
• We unconsciously apply a filter
• Paying attention to details requires conscious effort
© 2021 Cengage Learning, Inc.
Observation and Perception
LO3: Distinguish between observation and perception.
(2 of 2)
• Perception
– Interpreting sensory observations
• Not always accurate
• Does not always reflect reality
– Understanding limitations
• Helps improve observation skills
© 2021 Cengage Learning, Inc.
Eyewitness Observation
LO4: Distinguish between fact and opinion as they relate to eyewitness testimony.
(1 of 2)
• Observations made by witnesses
– Perceptions of witnesses can
be faulty
– Emotional states influence
perceptions
– Eyewitness accounts can be
valuable evidence
– Many factors affect accuracy
© 2021 Cengage Learning, Inc.
Eyewitness Observation
LO4: Distinguish between fact and opinion as they relate to eyewitness testimony.
(2 of 2)
• Eyewitness accounts
– Vary considerably from person to person
– Require discrimination between fact and opinion
– Used to sequence the events
• The Innocence Project
– Found that eyewitness identification contributed
to up to 70 percent of wrongful convictions
© 2021 Cengage Learning, Inc.
Improving Observation Skills
LO5: Describe ways to improve observation skills.
• Tips to improve skills
– Systematically examine the environment
– Turn off filters; act like data-gathering robots
– Avoid looking for patterns
– Concentrate on gathering information
– Leave interpretation until later
– Write down and photograph as much as possible
© 2021 Cengage Learning, Inc.
Interview Techniques
LO6: Describe the effective techniques that result in an accurate eyewitness interview.
(1 of 2)
• Conducting interviews
– Separate witnesses as soon as possible
– Help witnesses reconstruct what happened
– Provide minimal guidance
– Avoid interjecting biases
– Write down observations
– Ask questions to draw out
details
© 2021 Cengage Learning, Inc.
Interview Techniques
LO6: Describe the effective techniques that result in an accurate eyewitness interview.
(2 of 2)
• Identifying a truth or a lie
– A true account is consistent each time it’s told
– Lies are difficult to repeat exactly the same
• Methods to identify truths or lies
– Have witness repeat story several times
– Ask witness to recount story in reverse order
– Distract interviewee with questions
© 2021 Cengage Learning, Inc.
Summary
(1 of 2)
• Forensic science is the application of science
to help resolve legal matters
• Forensic scientists find, examine, photograph,
document, and evaluate evidence and provide
expert testimony to courts
• Observations at crime scenes are based on
sensory input and are affected by factors that
affect our ability to focus
© 2021 Cengage Learning, Inc.
Summary
(2 of 2)
• Perceptions are our brain’s interpretation of
our observations
• Facts are based on evidence; opinions are
based on what is perceived to have happened
• Observational skills can be improved by
limiting distractions and increasing awareness
• Effective interview techniques help a witness
recall events in an unbiased way
© 2021 Cengage Learning, Inc.