In a broad sense,
evidence refers to anything that is used to demonstrate or determine the
truth of a legal matter. It is the information for which a legal case
is built-on; evidence helps formulate a conclusion or judgment.
Types of Evidence:
There are four types of evidence: demonstrative, documentary, testimonial and real.
Real
Evidence: This form of evidence is any object or matter relevant to the
case in question. Real evidence is typically an object that is directly
involved in some aspect of the case. To be deemed admissible, real
evidence—similar to the other forms of evidence—must be material,
competent and relevant. Murder weapons, clothing or wrecked vehicles may
all be deemed real evidence when collected at the scene of a crime.
Real
evidence is authenticated in three ways—through identification of a
unique matter or object, by identification of the said object that is
made unique or establishing a chain of custody. For the evidence to be
deemed admissible it only has to be authenticated using one of the above
means.
Demonstrative Evidence: This form of evidence
illustrates a witness testimony. Demonstrative evidence is admissible
when it can fairly and accurately reflect the testimony and is otherwise
deemed unobjectionable—it is authenticated by the witness whose
testimony is being illuminated. The witness will identify salient
features of the evidence and testify that it accurately reflects what
the individual saw or heard during the particular occasion. Common
examples of demonstrative evidence may include: diagrams of the crime
scene, maps or animations.
Documentary Evidence: A form of real
evidence in document form, such as a contract. When a document is
offered to the court, it is authenticated in the same way as other forms
of real evidence—a witness must identify it or establishes a chain
custody for it.
Testimonial Evidence: This form of evidence is
the most basic form of evidence and the only kind that does not require a
prerequisite for its admissibility. Testimonial evidence consists of
witness testimonies, expert opinions and everything that is said in the
court. That being said, the witness or source providing the testimony
must be deemed competent by the court for the individual’s words to be
taken into account. In general, witnesses are deemed competent if the
individual meets the following requirements:
• The individual must, with understanding, take the oath of the court or an admissible substitute
•
The individual must have personal knowledge about the information he or
she is speaking on. The witness must have perceived something with his
or her senses that is relevant to the case.
• The witness must accurately remember what he or she perceived
• The witness must be able to communicate—lucidly—what he or she perceived.
How is Evidence Collected at a Crime Scene?
The
bulk of crime scenes are surrounded by crucial evidence that must be
collected for analysis and use in future prosecution efforts. The
process of collecting evidence is stringent; law enforcement officers
must employ exacting techniques to avoid tampering with the evidence.
Without use of these techniques, evidence may be lost, contaminated or
overlooked. Moreover, improper collection of evidence can be deemed
inadmissible in court or at a trial.
The following steps must be taken by a law enforcement officer when collecting evidence:
1.
The officer must secure and preserve the crime scene. Before evidence
can be collected, the scene must be taped-off and secured to prevent
further contamination. The crime scene must be formally established; a
perimeter must be secured to only allow the entry of necessary
personnel. The scene should also be photographed before any evidence is
collected.
2. The officer must put on gloves and protective
clothing to prevent contamination. The officers must first collect
evidence that is fragile or susceptible to the elements. For example,
hair, seminal fluid or other liquid evidence can be contaminated or lost
quickly.
3. The officers or investigators must use cotton swabs
or gauze to gather liquid evidence, such as blood. Items containing
seminal fluid or blood should be transported into paper bags to hold
moisture and prevent bacteria from forming. When collecting hair, thread
or fibers, the officers must use tweezers. Each piece of evidence must
be placed individually in sealed bags or containers.
4. For
fingerprints, the officer must employ a special powder that adheres to
the oil found on the human finger. When a print is detected it will be
“lifted” through the use of a special adhesive. This tape is placed on a
glass slide, marked and then transported into a sealed plastic evidence
bag.
5. For larger pieces of evidence, such as weapons or
clothing, the officers must use plastic gloves when transporting the
items. It is essential that the officers or agents at the scene do not
contaminate the evidence with finger prints, liquids, bacteria or
anything else that would manipulate the item or alter it’s surface.
