Basic Forensic Methods: Ch. 1 PDF

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Practical Crime Scene Processing and Investigation  Crime Scene Processing ● Crime scene processing is an inherent task and duty associated with nearly every investigation ● Few, if any, crimes are without some form of a “scene” ● Processing consists of the examination and evaluation of the scene and any evidence found there for the express purpose of documenting the scene context and recovering evidence ● There is no one right way to process a crime scene ○ each scene is unique and each scene has its own challenges ○ there are, however, basic key ingredients that make up a good processing methodology ● Key processing ingredients: ○ knowledge: a basic understanding by the crime scene technician of what they are trying to accomplish and why ○ skills and tools: the technician must have the appropriate equipment and be skilled with it in order to collect the various types of evidence they may encounter ○ methodical approach: the methods employed by the technician must be all encompassing and purposefully regular ○ flexibility: although methodical, the technician must also be flexible in order to deal with unique situations ○ coordinated effort: the entire team must coordinate their effort so everyone is pursuing the same goal  Evidence ● There are two basic forms of evidence: ○ testimonial evidence: admissions, confessions, statements by parties involved in the investigation ○ physical evidence: items and the condition of objects that are collected and/or documented ■ physical evidence will never lie

● we can misinterpret or be misled by it, but that is a human factor unassociated to the evidence itself ■ the consideration of physical evidence provides a factual framework that is, for the most part, irrefutable by anyone ● it provides objective information which will corroborate or refute testimonial evidence and investigative theories ■ having the pieces of the puzzle means little until we can put them back in order ● “The interpretive value of evidence is a function of time and the items surroundings”  Context ● By evaluating the context of evidence, we may be able to put the pieces in order and gain an understanding of how they came to be there ○ The goal of crime scene investigation is understanding the evidence, not simply collecting it ● Five ways context manifests itself: ○ 1) predictable effects ■ provides information as to the time of the incident based solely on the evidence itself ■ examples: insect activity at a death scene, rigor mortis, livor mortis ○ 2) unpredictable effects ■ changes that occur in unexpected or random ways ■ examples: actions of EMS or L.E. (opening doors, turning on lights, etc.), movement of evidence ○ 3) transitory effects ■ these are temporary things and tend to disappear quickly ■ examples: ice in a glass, heat from a cigarette, smells, wet shoe prints ○ 4) relational details ■ ability to physically place items in the scene ■ helps define a correlation between objects ■ crime scene sketches and the measurements help preserve this type of information

■ examples: a void pattern on wall surrounded by blood spatter, presence of a weapon near the victim ○ 5) functional details ■ operating condition of items in the scene ■ examples: the operability of a firearm, the lock on a door, an alarm set on the clock for a specific time  Crime Scene Integrity ● There are three basic threats the crime scene technician must recognize: ○ addition of material to the scene ■ the investigators and others end up creating evidence that didn’t exist ■ examples: shoe prints, fingerprints, fibers and hairs, cigarette butts, pop cans, coffee cups ○ destruction of material ■ the investigators and others end up destroying evidence or damaging its value ■ examples: trampled out dust prints in avenues of approach, bloodstains on the victim’s clothing, trampled dew trails in outdoor scenes, loss of evidence on the perimeter of the scene, loss of hairs and fibers on the body ○ movement of material ■ investigators and others end up moving material in the scene changing its context ■ examples: weapons moved away from suicide victims, lights turned on or doors and windows opened, staging actions by relatives (e.g., suicides or auto-erotic deaths)  Investigative Ethics ● The function of an investigation is to discover the truth ○ there is no other agenda ● Personal agenda and personal involvement will warp the investigator’s perspective ○ the investigator must remain a neutral and impartial professional

● To remain neutral and impartial, the investigator must: ○ investigate completely and thoroughly ○ consider and report all evidence, including exculpatory information ○ consider all viable hypotheses to explain the evidence ○ not be swayed by any lawyer...