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AJ 104
Crime Scene Evidence, Experiments, and Models
Freeze!!!
Introduction Real Evidence
Anything that can be perceived with the five senses, except, trial testimony.
Real Evidence Must be marked and formally
introduced into evidence The attorney who wishes to introduce
them must lay a foundation to establish the admissibility of the items in question.
Real Evidence Includes: Physical items
Guns, Knives Documents
Will be covered in the next chapter Exhibits
Models, renderings to depict a crime scene
Pictures Still, video, x-rays
Introduce Evidence In 4 Easy Steps (S.A.F.F.)
1. Show evidence to defense to examine (if desired)
2. Assign a number (the court clerk mark the evidence as People’s No. #)
3. Foundation is laid to establish the item is admissible.
4. Formal request is made to admit it into.
pg. 125
Crime Scene Evidence Items admitted must be authenticated
To show that an item is genuine To show is the same one described by
the witness The item needs to be the same condition
as it was found by the police unless tested
Careful handling of evidence and accurate report writing are crucial
WHY?
At the Crime Scene
Protect the evidence Restrict public access Do not clean the area Always better to have too many than
not enough Save everything of evidentiary value WHY?
Laying the Foundation
The series of questions an attorney asks witnesses in order to establish that a piece of evidence is admissible Have someone identify the object and
testify about where the item was found What has been done since it was taken
into the custody? WHY?
Marking & Packing, & Sketching Once an object is identified and can be
used as evidence, it should be marked at the time it is collected Before collecting and packaging , make a
detailed recordation of the crime scene/collection
Mark with the officer’s initial’s They should not be placed where they may
interfere with lab results Exercise caution preserve fingerprints,
blood, DNA, etc.
Marking & Packing, & Sketching
When possible, try to do as many f the following as possible:
Make sketches of the location (to scale) indicating where the object was found Locations of doors, windows,
Take photos of the area Make detailed notes
Real or Hollywood?
Real or Hollywood?
Real or Hollywood?
Crime Scene Sketch
Crime Scene Sketch
The proper packaging of evidence is extremely important Evidence needs to be preserved for trial Care must be taken not to damage,
evaporate or contaminate Each piece of evidence must be packaged
individually & labeled on the outside. Leave enough space for everyone who
handles the evidence will indicate the date, time, and reason for handling it.
Chain of Custody Also called “continuity of possession” It is necessary to account for
everyone who has had possession of the evidence in order to show the judge and jury that the evidence has not been tampered with.
Pg. 129 (sketch)
Scientific Evidence
Forensics Can be used to established the
elements of the crime Conclusively associate the defendant
with the crime, Help reconstruct the crime
Types of Cases Using Scientific Evidence Police are likely to clear a case when
scientific evidence is used. Jurors give scientific evidence serious
consideration, but is not the key element
2/3 of their cases involve: Drugs Narcotics Drunk Driving
Types of Cases Using Scientific Evidence
The next most common categories were: Firearms Blood & Bloodstains Semen
Forensic evidence was used in nearly all murder and drug possession cases.
Scientific Evidence, Laying the Foundation The foundation for the introduction of
scientific investigation involves answering three questions: Is this a valid scientific test? Was accurate equipment used for the test? Was this test performed in an appropriate
manner by a qualified person? Both sides will call their expert witnesses
to challenge the validity of the test.
Commonly Accepted Scientific Tests
Many tests are so well established that they are admitted at trial without a challenge to their validity. Identification of Controlled Substances Identification of Firearms Blood Alcohol Blood Typing DNA Testing
Tests Not Commonly Accepted Scientific tests must be accepted in
their field before the courts are willing to allow their use at trial Polygraph
The high frequency of inconclusive results makes the courts distrust the results of a polygraph
Hypnosis It is still a concern of the court being in a
trancelike state and being unconsciously responsive.
Experiments
Screens out all extraneous variables so that the experimenter ca measure the impact of one factor. Few experiments are introduced in
court