Post on 21-Dec-2015
Bellringer:Answer the following in your notes
Police investigating an apparent suicide collect the following items at the scene:a note purportedly written by the victima revolver bearing very faint fingerprintstraces of skin and blood from under the victims
fingernails
What units of the crime laboratory will examine each piece of evidence?
CSI mistakes
CSI effect
Expert vs. Lay Witness
Functions of the Forensic Scientist
Forensic Scientists rely primarily on scientific knowledge. However, only half the job is performed in the laboratory while the other half takes place in the courtroom.
These functions fit into three categories:
1. Analyzing of Physical Evidence
Physical evidence is less likely to be compromised or tainted by human emotions than eyewitness accounts from victims or witnesses
the analysis of physical evidence involves adherence to: strict guidelines systematic collection organization and analysis of information OF INFORMATION (THE SCIENTIFIC METHOD)
an understanding of admissibility of evidence is important Frye, Daubert, Kumho, Coppolino
2. Providing Expert Testimony
Forensic Scientist are called on to evaluate evidence when the court lacks the expertise to do so
Must establish competency by citing educational degrees, number of years of occupational experience membership in professional societies, special courses taken and any professional articles or books published.
Cross-examination may reveal weaknesses in background and knowledge
Demeanor and ability to explain scientific data clearly and logically to a judge and jury of non-scientists
Must be an advocate of truth and not take a side
3. Providing Training
Evidence must be properly recognized, collected and preserved if it is to have value.
Many, but not all crime laboratories keep trained “evidence technicians”.
Sometimes a patrol officer or detective collects the evidence.
All officers engaged in fieldwork must be familiar with evidence collection.
These people are trained by laboratory staff through extensive personal contact, lectures, laboratory tours and/or dissemination of manuals.
Witnesses vs. Physical Evidence
Most witnesses do not intentionally lie on the witness stand
Human observation is limited by memory, suggestion, and interpretation
Memories can be confused or altered, but physical evidence stays the same
bunny Effect video
What is the first critical step of crime-scene investigation? Why is this step so important?
List a situation in which a warrantless search may be justified.emergency circumstancesprevent immediate loss or destruction of evidencesearch of a person and property within the immediate
control of the person provided it is made incident two a lawful arrest
consent by parties involved
The Crime Scene
Forensic science begins at the crime scene;
It is imperative that physical evidence be recognized and properly preserved.
Securing and Isolating
The first officer arriving at the scene must:•preserve and protect as much as possible
•Priority given to those needing medical assistance and to arresting the perpetrator.
•Once the scene has been secured, the lead investigator determines the boundaries of the scene and establishes the perpetrators path of
entry and exit.
Securing Crime scene
Properly secured and protected firstthorough search to be sure there are no suspects
or physical danger
safety PPE (personal protective equipment)
Need to protect yourself: head, eyes, lungs, hands, feet, and occasionally your entire bodyGlovesrubber booties for your feetGoggles or a face shieldRespiratory filter to protect lungs
Recording the scene
• Notes, sketching and photography are used.
• These will aid the investigation and be presented at trials.
• It is becoming more common to use videotape as well.
Photography should include:
photograph the shoes of everyone at the scene
Overview of surrounding area
Points of exit and entry
If indoors, each wall area should be shown
If there is a body, photos should show its position, injuries and any weapons near by
The surface beneath the body
All items of physical evidence including close-ups
A ruler may be inserted near objects whose size may be of significance.
Panoramic views can be produced by pasting together images.
**If any items are moved, added or have changed position photograph may not be admissible as evidence**.
SketchingSketching is done after the photographs are taken.
A rough sketch is done first
Objects are located by distance measurements from two fixed points.
Evidence is given letter designations
A legend is included below the sketch
A compass designating north is shown
A finished sketch contains all of the information in the rough sketch. It is drawn with presentation in mind. Sometimes CAD is used
Rough Sketch
Finished Sketch
Notes Note taking is a constant activity throughout the
processing of the crime scene
Notes should include: A detailed description of the scene The location of items of physical evidence recovered The time the physical evidence was discovered, by
whom, how and by whom it was packaged and marked. Other noteworthy sights, sounds, smells, etc. This record may be the only source of information for
refreshing one’s memory months, perhaps years, after a crime has been processed.
Conducting a search Must be thorough and systematic
Overlooked evidence can lead to accusations of a cover-up attempt
How one proceeds depends on the locale and size but must include all probable points of entry and exit
What to search for is determined by the type of crime, for example in a homicide the focus will be on a search for the weapon; a burglary: tool marks at the point of entry
In most cases a search for latent fingerprints is required
Careful vehicle searches are also done
Crime scene search patterns
Locard’s Exchange Principle
Source: http://www.virtualsciencefair.org/2004/fren4j0/public_html/trace_evidence.htm
"Every Contact Leaves a Trace"
• The value of trace (or contact) forensic evidence was first recognized by Edmund Locard in 1910.
• He was the director of the very first crime laboratory in existence, located in Lyon, France.
The Locard’s Exchange Principle:
"with contact between two items, there will be an exchange."
For example, burglars will leave traces of their presence behind and will also take traces with them. They may leave hairs from their body or fibers from their clothing behind and they may take carpet fibers away with them.
Physical evidence
How does the textbook define physical evidence?Physical evidence is any object that can
establish that a crime has been committed or can link a crime and it's victim or a crime and it's perpetrator.
Forensic science starts at the crime scene where evidence is recognized and properly preserved.
Steps in evidence collection
1. Photography (www.mycrimekit.com)
2. Sketches
3. Conduct a systematic search for evidence
4. Collect physical evidence
5. Maintain the chain of custody
6. Obtain standard reference samples
7. Submit evidence to the laboratory
Chain of CustodyEVERY person who has come into contact with the
evidencehandledexamined
Acts as a “paper trail”
Failure to do so:lead to questions regarding the authenticity and
integrity of the evidence and the examinations
When evidence is is analyzed there must be a new seal made
Procedures for collecting evidence
ProceduresIdentify the evidence
(is it evidence, could it contain evidence?)Decide which type of packaging would be
the most appropriate (plastic pill bottle, manila envelope, paper
bag, a sealed container?)Record where evidence was found
(living room, northeast corner of park, etc.)
Label the evidence(victim’s shirt, hat)
Date and intial (you will keep a record of when you
collected the evidence and that you collected)
•Tag the evidence for identification•Seal the evidence• (put tape on it to make sure no one
else has opened/compromised the sample)
•Fill out an evidence submission form•Maintain records on chain of custody• Every person that handles the
evidence needs to log it.
Types of physical evidence
• Paint
• Glass
• Explosives
• Ballistics
• Dust & Dirt
• Impression evidence
• Fracture matches
• Wounds
• Questioned documents
• Insects
• DNASkeletal remains
• Body fluids
• Hairs & Fibers