Forensic Science

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.

Crime Scene Vocabulary

Crime Scene VocabularyPerpetrator: a person who commits an offense or

crime.Buccal Swab: Swab of inner portion of cheek (cells

provide DNA)Chain of Custody: A list of all persons who came

into possession of an item of evidence.Control: Physical evidence whose origin is known

(blood or hair from a suspect) that can be compared to crime-scene evidence.

Crime Scene VocabularyPhysical evidence: encompasses any and all

objects that can establish that a crime has been committed or can provide a link between a crime and its victim.

Rough sketch: A draft representation of all essential information and measurements at a crime scene. Drawn at the crime scene.

Finished sketch: A precise drawing of the crime scene, usually drawn to scale.

So, you might want to become a CSI.

http://www.youtube.com/watch?v=1B-eqVp3L7k&feature=related

https://www.youtube.com/watch?v=jcypaqcKesU

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.

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.

Crime Scene Personnel

The MEDICAL EXAMINER (if a homicide) determines a preliminary cause of death.

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.

Crime Scene Personnel

Processing the Crime Scene1. Secure and Isolate the Crime Scene.– It is the responsibility of the first officer arriving

on the scene of a crime to take steps to preserve and protect the area to the greatest extent possible.

– Boundaries of the scene must be determined.– The perpetrator’s path of entry and exit need to

be secured.

Processing the Crime Scene2. Record the Scene– Investigators only have a limited amount of time

to work a crime scene in its untouched state.– The crime scene needs to be permanently

recorded and documented.– Photography, sketches and notes are the 3 main

ways to do this.

Processing the Crime Scene– Photography• Objects must not be moved before they are

photographed from ALL angles.• If there was a body involved, close-ups of the injuries

and any weapons need to be photographed.• Once the body is removed the ground beneath the

body needs to be photographed.• If the size of an item is significant, a ruler (or other

scale) may be used near the object.• The use of videotape is also becoming increasingly

popular.

Processing the Crime Scene– Sketches• Once photographs have been taken, the crime-scene

investigator will sketch the scene.• First a rough draft is made using accurate dimensions

of the scene and showing the location of all objects that are important to the case.• Distance is measured using 2 fixed points (walls, doors

etc).

Processing the Crime Scene– Sketches• All measurements are made with a tape measure.• Letters or numbers are assigned to the objects.• A legend correlates the letter/number to the object.• The finished sketch is drawn carefully using templates

or computer software (CAD) by a skilled individual – it needs to look good!

Processing the Crime Scene– Notes• Note taking must be constant throughout the

processing of the crime scene.• Includes details of EVERYTHING.• This written record may be the only source of

information to refresh memories months or even years after the crime.• Tape-recording notes at the scene or narrating a

videotape works much faster HOWEVER at some point the tapes need to be transcribed into a written document.

Review Questions1. The term _____ encompasses all objects that can establish

whether a crime has been committed.2. All unauthorized personnel must be _____ from crime

scenes.3. Three methods for recording the crime scene are _____,

______, and ______.4. The most important prerequisite for photographing a

crime scene is to have it in an ______ condition.5. An investigator need only draw a _____ sketch at the

crime scene to show its dimensions and pertinent objects.

Processing the Crime Scene3. Conduct a Systematic Search for Evidence– The search for physical evidence at a crime scene

must be thorough and systematic.– It is important that it be done at once.– The locale and size of the area is going to dictate

which method is used to do this search.

,Strip or line or quadrant

Processing the Crime Scene4. Collect and Package Physical Evidence– Physical evidence has to be handled and processed in

a way that prevents any change from taking place between the time it is removed from the crime scene and received by the lab.

– Small items can be collected and packaged easily.– If the item is lodged in a large structure common

sense must be used:• If it is a building wall, care needs to be taken to extract it,

doors can be unhung, appropriate tools must be used.

Processing the Crime Scene4. Collect and Package Physical Evidence– Each different item or similar item collected at

different locations MUST be placed in separate containers.

Processing the Crime Scene5. Maintain Chain of Custody– Continuity of possession must be established

whenever evidence is presented in court as an exhibit.

– Standard procedures include completing an evidence submission form.

– Every person who handled or examined the evidence must be accounted for.

– The chain of custody should be kept to a minimum.

Processing the Crime Scene6. Obtain Controls– Examination of evidence often requires

comparison with a known standard or control.– Can be obtained from the victim, suspects, or

other sources.– Bloodstained evidence must be accompanied by

whole blood or buccal swab controls.

Processing the Crime Scene7. Submit Evidence to the Laboratory– Final step where evidence is delivered to the

forensics laboratory for processing.

• The techniques needed to collect evidence from a crime scene requires a highly skilled technician.

Review Questions6. A detailed search of the crime scene for physical evidence

must be conducted in a ______ manner.7. Each item collected a the crime scene must be placed in a

_____ container.8. The possibility of future legal proceedings requires that a

_____ be established with respect to the possession of physical evidence.

9. Most physical evidence collected at a crime scene will require the accompanying submission of _____ material for comparison purposes.

10. Technicians working the crime scene need to be __________.

What evidence would you collect?

Any Questions?