Chapter 3: Crime Scene Investigation and Laboratory Analysis of Biological Evidence

Requires: Crime scene examination▪ Scene security, documentation, collection and

preservation of evidence Laboratory analysis▪ Utilizes scientific techniques for evidence

examination, identification of biological fluids, and the comparison of individual characteristics

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Protecting and securing the scene: Duty of the first officer on the scene Only authorized personnel Use log sheet Obtain medical attention if needed Proper supplies and devices must be

utilized▪ E.g. Disposable suits, face mask, disposable

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Documentation Sketch▪ Rough and Finished

Photographs ▪ Use photo log sheet▪ Use scale

Video

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Chain of Custody- lists custody information at every point in time when evidence is handled or transferred

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Recognition of biological evidence▪ Corpus delicti evidence▪ Victim-to-perpetrator linkage evidence▪ Victim-to-scene linkage evidence▪ Perpetrator-to-scene linkage evidence▪ Case-to-case linkage evidence▪ Modus operandi

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Locard Exchange Principle: Cross-transference of evidence occurs

when a perpetrator has any physical contact with something or someone else

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Searches Alternate Light Source (ALS) Types▪ Spiral▪ Grid▪ Strip▪ Quadrant/Zone

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Collection Only done after documentation is complete Consider collecting entire item if small

enough or mobile Considerations▪ Bloodstain pattern evidence▪ Multiple analysis of evidence▪ Trace evidence▪ Control samples▪ Size of the stain▪ Wet Evidence

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Packaging and Transportation Goal: protect and preserve evidence Avoid heat and humidity Package items separately Allow wet items to air dry Use paper! Label properly and seal

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Identification of biological evidence

Comparison of individual characteristics of biological evidence

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Class Characteristics Can be placed into a category with other

similar materials

Individual Characteristics Evidence possesses characteristics that

share a common origin with a reference sample

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Final steps: Reporting results Expert testimony

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