Transcript crime scene

Forensic Scienceapplication of science to legal questions
(criminal or civil)
T. Trimpe 2006 http://sciencespot.net
Crime Scene Vocabulary
CRIME SCENE: Any physical location in which a crime has occurred or is
suspected of having occurred.
PRIMARY CRIME SCENE: The original location of a crime or
accident.
SECONDARY CRIME SCENE: An alternate location where
additional evidence may be found.
SUSPECT: Person thought to be capable of committing a crime.
ACCOMPLICE: Person associated with someone suspected of committing a crime.
ALIBI: Statement of where a suspect was at the time of a crime.
Source: http://www3.sc.maricopa.edu/ajs/crime_scene_technician.htm
Types of Evidence
Testimonial evidence includes oral or written statements given to police as well as
court testimony by people who witnessed an event.
Physical evidence refers to any material items that would be present at the crime
scene, on the victims, or found in a suspect’s possession.
Trace evidence refers to physical evidence that is found in small but measurable
amounts..
What will evidence collected at a scene do for the investigation?
• May prove that a crime has been committed
• Establish key elements of a crime
• Link a suspect with a crime scene or a victim
• Establish the identity of a victim or suspect
• Corroborate verbal witness testimony
• Exonerate the innocent
• Give detectives leads to work with in the case
Source: http://www3.sc.maricopa.edu/ajs/crime_scene_technician.htm
Locard Exchange Principle
 when two objects come into contact with one
another, an exchange of matter takes place.
 Physical evidence can link suspect, victim, crime
scene, and objects to one another
Direct Evidence - first hand observations
• Eyewitness accounts
• Video
• Confessions
Circumstantial Evidence – indirect evidence
that can be used to imply a fact but that does not
directly prove it.
• Physical or biological evidence
Class Evidence– narrows an identity to a group
of persons or things
Individual Evidence – narrows an identity to a
single person or thing
• Can only belong to one person
Categorize the following:
DNA
Blood type
Fingerprints
Crime Scene Personnel
POLICE OFFICERS are typically the first to arrive at a crime scene. They are
responsible for securing the scene so no evidence is destroyed and detaining
persons of interest in the crime. They will also separate and hold available
witnesses for detectives.
The CSI UNIT documents the crime scene in detail and collects any physical
evidence.
The DISTRICT ATTORNEY is often present to help determine if any search
warrants are required to proceed and obtains those warrants from a judge.
The MEDICAL EXAMINER (if a homicide)may or may not be present to
determine a preliminary cause of death. *usually a pathologist.
SPECIALISTS (forensic entomologists, anthropologists, or psychologists) may be
called in if the evidence requires expert analysis.
DETECTIVES interview witnesses and consult with the CSI unit. They
investigate the crime by following leads provided by witnesses and physical
evidence.
Source: http://science.howstuffworks.com/csi.htm
Seven S’s of Crime Scene Investigation
1.Securing the Scene.
• Log who comes in the secured area
2.Separating the Witnesses
3.Scanning the Scene
4.Seeing the Scene (photos, videos)
5.Sketching the Scene
6.Searching for Evidence
• Grid, linear or spiral pattern search
• Vacuum cleaner with clean bag, tweezers
7.Securing and Collecting Evidence
Crime Scene Sketches
1. Rough- a draft representation of all essential info
and measurements at a crime scene
2. Finished- a precise rendering of the crime scene
using CAD (computer-aided drafting) drawn to scale
require
•
•
•
•
•
•
Title or caption
Legend of abbreviations
Numbers of letters used
Designate North direction
Measurements from 2 fixed points
Documentation block with case number,
offense type, victim’s names, location, date
and time, and sketcher’s name
Packaging Evidence
1.Create proper size bindle (“druggist fold”)
2.Place bindle inside a plastic or paper bag.
3.Fill out Evidence/Chain of Custody Log
4.Fold bag closed.
5.Place a seal over the folded edge of the
evidence bag.
6.Sign and date seal.
Chain of Custody
• Is a list of all persons who come in possession of
an item of evidence
• Must be established whenever evidence is
presented in court
– The evidence container must be marked for
identification
– The collector’s initials should be placed on the seal
– If evidence is turned over to another person, the
transfer must be recorded
Obtaining Reference Samples
• A standard/reference point is physical
evidence whose origin is known, such as
hair from a suspect that can be compared
to a hair found at the crime scene
– Exists with blood, glass, soil, fibers, paint
chips, etc
Alphonse Bertillon
(1853-1914)
• “Father of Anthropometry”
• Developed a system to distinguish one
individual person from another based on
certain body measurements.
Edmond Locard
(1877-1966)
• “Father of the Crime Lab”
• In 1910, he started the 1st crime lab in an
attic of a police station in Paris, France.
• With few tools, he quickly became known
world-wide to forensic scientists & criminal
investigators & eventually founded the
Institute of Criminalistics in France.
• His most important contribution was the
“Locard’s Exchange Principle”
Frye Standard
(1923)
For the results of a scientific
technique to be admissible, the
technique must be sufficiently
established to have gained “general
acceptance” in its particular field.
Collection of experts called in to testify
about the validity of scientific issues
Books and papers written on subject
reviewed and discussed.
18
Federal Rules of Evidence
(1975)
• RULE 702. TESTIMONY BY EXPERT WITNESSES
• A witness who is qualified as an expert by knowledge, skill,
experience, training, or education may testify in the form of an
opinion or otherwise if:
(a) the expert’s scientific, technical, or other specialized
knowledge will help the trier of fact to understand the evidence or
to determine a fact in issue;
(b) the testimony is based on sufficient facts or data;
(c) the testimony is the product of reliable principles and
methods; and
(d) the expert has reliably applied the principles and methods to
the facts of the case.
Federal Rules of Evidence
To be admissible:
Must be…
Probative:
Material:
Daubert Ruling
(1993)
• “general acceptance” or Frye standard no
longer absolute prerequisite.
• Trial judge given the task of ensuring an
expert testimony rests on a reliable
foundation, is relevant to case, and is not
repetitive, inflammatory or unnecessarily
confusing. (gatekeeper)
What evidence would you collect?
Circle the items you would collect and then explain how you would
use them to gather clues about the crime.
Mock Crime Scene: http://www.masss.gov