The Crime SceneHonors Forensic Science

I. Processing the Crime Scene

Crime Labs “run” on physical evidence

Physical Evidence = any and all objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator

To be effective, evidence must be:

Recognized Collected and processed properly

Collector must be selective using knowledge of crime lab techniques, capabilities and limitations

Crime labs do not solve crimes

Many jurisdictions have specialized teams to conduct crime-scene searches

Not all crime scenes require retrieval of physical evidence

II. Secure and Isolate Crime Scene

First officer(s) on scene should:

Provide medical assistance, if needed, to victims

Arrest perpetrator if present Preserve and protect area as much as

possible

II. Cont’ d

Exclude all unauthorized personnel from scene

Isolate area using ropes, tape, barricades, guards, etc.

Lead Investigator should:

Determine boundaries Determine perp’s path of entry and exit Document obvious items Conduct initial walk-through Develop examination strategy

Record the Scene

Must document the crime scene in original state

Information used in investigation and in court

Monetary limitations may determine method used to document the scene

Photography Must be in unaltered condition Crime scene photographed completely Items of physical evidence

photographed to show position and location; close-ups to show detail

If size is important, include a measurement scale in photo for reference

Videography Can be used to augment photography Can narrate events on videotape Does not replace photography

Sketches

Rough Sketch

Containing an accurate depiction of the dimensions of the scene and showing the location of all objects having a bearing on the case

Rough sketch should include; Recovered items of physical evidence Distance measurements of items (use 2

fixed points) Legend Compass heading designating north

Finished Sketch

A precise rendering of the crime scene, usually drawn to scale

Often prepared with aid of templates and drafting tools

Reflect same information as rough draft

CAD programs often used

Notes

Must be a constant activity Should include detailed written

description of scene Detailed description of evidence:

location of items, time item discovered, by whom, how and by whom it was packaged, etc.

Notes often only written record of details

Tape-recording can be advantageous, but still should be transcribed into a written document

Conduct Systematic Search

Thorough and systematic, even if seems unnecessary at the time

How crime scene is searched depends on type of crime, local and size of scene, # of collectors, etc.

Collect massive objects to microscopic traces

Important to collect possible carriers of trace evidence as well as obvious items

Portable vacuum cleaners helpful

Medical examiner may also provide evidence

Medical examiner may collect and forward: Victim’s clothing Fingernail scrapings Head and pubic hairs Blood (for DNA typing) Vaginal, anal, and oral swabs Recovered bullets from body Hand swabs from shooting victims

Collect and Package Physical Evidence

Prevent change

Change can arise from contamination, breakage, evaporation, accidental scratching or bending, or loss through improper or careless packaging

Maintain evidence in original condition if possible

Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevent contamination

Maintain Chain of Custody

Chain of custody – list of all persons who came into possession of an item of evidence

Must be established whenever evidence is presented in court

Adhere to standard procedures Keep to a minimum

Obtain Controls

Examination of evidence often requires comparison with known standard or control

Control = physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime scene evidence

Quality and quantity of controls may help determine evidential value of crime-scene evidence

Controls must be treated with equal care as actual evidence

Submit Evidence to Lab

Usually submitted personally or by mail shipment

Must be accompanied by evidence submission forms

List of tests to be performed on each item

List of items submitted

Crime Scene Safety

International Association for Identification Safety Committee Gloves Particle masks/respirator, goggles, face

shield Be alert to sharp objects Use biohazard bags Note taking done with uncontaminated

gloves No eating, drinking, smoking, etc. at

crime scenes

Legal Considerations

Fourth Amendment – Prohibits unreasonable search and seizure

Mincey v. Arizona Michigan v. Tyler When time and circumstances

permit, obtain a search warrant before investigating and retrieving physical evidence at crime scene