forensic science 4 part 2

what is the steps; search for evidence?

a thorough and organized search is done to locate all potential evidence

the size and layout of a search area determine the way the investigators will search for evidence. investigators choose one of the following patterns to cover a crime scene;

strip or line search pattern, grid search pattern, spiral search pattern, wheel/ray search pattern, quadrant/ zone search pattern

what is strip/line search pattern?

• one or two investigators start at the boundary at one end of the scene and walk across to the other side. Then they move a little further along the boarder and walk straight back to the other side.

• best used in scenes where the boundaries are well established, bc the boundaries dictate the beginning and the end of the search lines.

what is the grid search pattern?

• two people performing line searches that originate from adjacent corners form perpendicular lines.

• very thorough method, but boundaries need to be well established

what is spiral search pattern?

• one person

• the investigator moves either in an inward spiral from the boundary to the center of the scene or in an outward spiral from the center to the boundary.

• helpful method bc the searcher is moving from an area light with evidence to an area where more evidence will most likely be found.

• can easily locate footprints, leading away from the scene in any direction

• however, doing a perfect spiral is difficult, evidence could be missed

what is the wheel/ray search pattern?

• several people moving from the boundary straight toward the center of the scene (inward) or the opposite (outward)

• not preferred method bc the areas between the “rays” are not searched

what is the quadrant/zone search pattern?

• the quadrant/zone method divides the scene into zones or quadrants and team members are assigned to search each section.

• those sections can be subdivided into smaller sections

• method best suited for scenes that cover a large area

what should be tagged as evidence?

anything can be considered as evidence, but they cant all be brought to the lab for analysis, bc the scientists would be overwhelmed. Its up to the investigator to recognize what is pertinent to the case and know what test can be done

if relevant, evidence can ?

• create a link between a suspect and crime scene

• support or disprove a statement (alibi)

• identify guilty or victim

• provoke a confession

when is a search warrant not necessary?

• emergency situations (someones life in danger, evidence found in this circumstance can be used)

• impending loss of evidence ( to save evidence from an impending destruction of evidence, ex: fire)

• lawful arrest (when a suspect is arrested, his property is open to search for evidence)

• consented search (when you consent to a search of your property)

what is the step; secure and collect evidence?

each evidence needs that proper packaging, labeling, and chain of custody procedures are followed to preserve evidence for analysis

what is the first step of collecting evidence?

collecting fragile evidence and evidence that will most likely be damaged, lost, displaced or contaminated (ex: outdoor crime scene)

for fingerprints, tool marks, fibers/hair, carpets/furniture, how are there evidence gathered from the crime scene and packaged to be sent to the lab?

• Fingerprints; photographed first, then lifted or transfered to a material that investigators can take w them to the crime lab.

• tool marks/shoeprints/tire impression; photographed, then cast or lifted

• fibers/hair; found w alternative light sources and collected w tweezers

• carpets/furniture; vaccumed w fresh bag/filter for each area

  packaging= each piece is packaged seperately to avoid cross-contamination.

  Dry trace evidence goes in paper folds or envelopes.

  Wet biological evidence is dried and placed in non-airthight paper bags.

  Liquids go in unbreakable, airtight containers.

explain what is a chain of custody and why is it so important?

the chain of custody is a documented record that shows every person who has handled a piece of evidence from its discovery to its presentation in court. It is important to keep the chain of custody intact in order to ensure that the evidence is admissible in court.