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Book CoverHere

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Chapter 3

THE CRIME SCENEDiscovery, Preservation, Collection, and Transmission of Evidence

Criminal Investigation: A Method for Reconstructing the Past, 7th Edition

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The Crime Scene

• Defining the Limits of the Crime Scene• The Crime Scene as an Evidence Source

– The CSI Effect• Opportunity for Discovery• Purpose of Search• Arrival of the First Police Officer • Arrival of the Investigator• Other Sources of Physical Evidence

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The Crime Scene as an Evidence Source

1. An offender brings physical evidence to the crime scenea. Tools, weapons, flammable fluid, hard drives, messages on cell phones, etc.

2. An offender may leave evidence behinda. Fingerprints, tool marks, shoe prints, bullets, blood-spatter patterns, etc.

3. Some evidence is unavoidably left behinda. Ransom notes, recorded tapes, etc.

4. Investigator’s observations and interviews might develop intangible evidence.

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The CSI Effect

• From a forensic scientist’s perspective, CSI shows have been both meaningful and detrimental

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Search Warrants• Exceptions allowed by the Court

– Consent to search• Must be given voluntarily by a person reasonably

believed to have control over and legal access to the premises

– Emergency situations:• Those involving an attempt or opportunity to carry off or

destroy evidence. To support this contention, belief must meet the standard of probable cause.

• Those involving threats to safety or life. In these cases, a lower level of proof — reasonable suspicion — is acceptable.

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Discovery of Physical Evidence• Overview, Walk-Through, and Search• Recording Conditions and Evidence Found

– Notes – Videography– Photographs– Sketches (Computer Aided Design – CAD – systems)

• Collection and Preservation – Preservation: Legal Requirements

• Identification • Continuity of Possession/Chain of Custody

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Trace Evidence

• Differs from ordinary physical evidence mainly because of its small size; calls for special methods

• Three techniques:– Vacuuming– Shaking– Sweeping and adhesion to tape

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Preservation — Legal Requirements

• Certainty of the identification• Continuity of possession — the chain of

custody of each item of evidence

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Preservation and Collection• Preservation – Scientific Requirements & Means• Collection – Scientific Requirements & Means

– Scientific Requirements– Control of Variables

• Background Material• Sample Sufficiency• Means• Tools• Containers

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Collection – Special Considerations

• Trace Evidence• AIDS and Hepatitis C

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Transmission of Evidence to the Laboratory

• Best done in person for legal and scientific reasons

• In the case that this is not possible, the U.S. Postal Service or UPS

• Must be packaged properly• Special concerns in high-profile cases

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Finding Physical Evidence by Canvassing

• Interviewing neighbors or companions of suspects– May produce writing samples, trace evidence, or

DNA samples from where suspect visited

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Conclusion

• The crime scene is a critical component of the investigation

• Do not ignore contribution of patrol officers and first responders

• Knowledge of crime scene activities is an important aspect of the investigative function