Download presentation
Presentation is loading. Please wait.
Published byTobias Nicholson Modified over 8 years ago
2
Evidence : Something that tends to establish or disprove a fact. Examples of evidence: › Documents › Testimony › Other objects
3
Testimonial vs. Physical Evidence Testimonial: what is said in court by a competent witness; also called direct evidence or prima facie evidence Physical: tangible items that tend to prove some material fact; also called real evidence.
4
Eyewitness accounts can provide important evidence leading to the arrest of a criminal. Juries are HEAVILY influenced by eyewitness identification. QUESTIONS: How accurate are eyewitnesses? What might influence their accuracy?
5
Eyewitnesses can make perceptual errors for many reasons: › Crime scene could have been dark › Encounter could have been very brief › Weapon could have diverted with witnesses attention Errors in the memory process are very common! TIME is a huge factor! › Time between the actual event and questioning
6
What could lead someone to say something? Could seeing someone who looks like someone affect recall from memory? Could a person persuade someone to say something this is untrue? How?
7
Police must be very careful in choosing an eyewitness who is reliable…which is hard to tell from a few questions Important points to consider: › What type of crime and what was seen › Serious crimes vs. not so serious crimes › Age of eyewitness and affected memory › Interviewing techniques and retrieval of information
8
What type of crime and what was seen › Witnesses more likely to accurately remember characteristics such as sex and hair color, more than age, height, and specific race. Serious vs. not so serious crimes › Victims of serious crimes are more likely to remember every detail because they relive the incident often. › Weapons/threats tend to sharpen focus and make information more easy to recall. › Any kind of stress tends to narrow focus.
9
Age of eyewitness and affected memory › Children tend to not remember as well as adults. Accuracy of child = interviewing technique. › Older adults have poorer eyesight and hearing which could affect memory and make the information less accurate. › Learning disabilities, mental disorders, alcohol, drugs, or head injuries weaken memory and make recall difficult.
10
Interviewing techniques and retrieval of information › Research shows that eyewitnesses answer questions better about the situation than what a person looked like. › Open-ended questions will provoke better responses What was the offender wearing? Vs. What color was the offender’s shirt? Avoid leading questions: Was the offender’s shirt red? These questions limit accuracy.
11
Other factors to consider: › Did the witness know the accused and what kind of relationship was established? › How much time has passed between the offense and the identification? › Has the witness already identified/failed to identify the defendant? › Has the witness identified someone else?
12
Most known cases of an innocent person being convicted happened because of a mistaken eyewitness identification.
13
Most interested in physical evidence because it is “physical”! You, as a scientist, can put your hands on it! Physical evidence takes on many forms because it is virtually unlimited. Some examples: › Something as large as a building › As fleeting as an odor › As small as a hair › Or submicroscopic, such as DNA evidence
14
Much more reliable than testimonial evidence Indirect evidence : evidence that does not prove a fact; most evidence Circumstantial evidence : evidence that implies a fact or event without actually proving it. (The more the better!) › Possession of a controlled substance › Driving under the influence
15
Value of Physical Evidence: › Can prove a crime has been committed and set the scene for the investigation › Back up a witness testimony or prove it false › Can link a suspect with a victim or with a crime scene › Can determine the identity of people associated with a crime › Can allow investigations to reconstruct a crime
16
Role of the Forensic Scientist and Physical Evidence: › Collect and submit physical evidence for testing in a lab setting › Determine links between the evidence, the victim, the crime scene, and the suspect › Determine if collected evidence is relevant to the crime
17
Testing Physical Evidence Unknown/questioned evidence : material that has been collected from a known location but is of unknown origin Known/control evidence : material that comes from a proven or known source Once samples are all known, it is important for forensic scientists to reconstruct the crime scene so they can form a more accurate opinion of what happened/answer questions about events.
18
When reconstructing the scene, this allows for all physical evidence to be put into a proper place and prove its relevance to the investigation. Reconstruction uses the forensic scientists, crime scene investigators, detectives and other law enforcement officers, and medical examiners.
19
The best evidence is that which can be linked to a unique, single, specific source; Individual evidence. › Fingerprints, handwriting, DNA patterns, or sometimes physical matches like broken glass Most evidence is considered class evidence, which means it is associated with a common group of items. › Blue jeans, tennis shoes, etc.
20
To prove probative value (the ability of evidence to prove something that is material to a crime), forensic scientists must find as many different types of objects as possible to link the suspect to the crime. › Dirt on a shoe, glitter on a pair of jeans, etc.
Similar presentations
© 2024 SlidePlayer.com Inc.
All rights reserved.