Crime Scene Investigation: A Comprehensive Guide

Posted on Apr 30, 2024 in Medicine & Health

Exam 1 Material

  • What is crime scene processing?

    • The examination and evaluation of the scene and any evidence found there for the express purpose of documenting the scene context and recovering the evidence.

  • Know the following, including examples: predicable effects, unpredictable effects, transitory effects, relational details, functional details

    • Predictable Effects

      -> Changes to the scene that occur with some rhythm or regularity
      • Body Decay
      • Insect Life Cycles

    • Unpredictable Effects

      -> Changes that occur in an unexpected or random fashion
      • Alteration of the original scene and evidence/ can lead to misinterpretation 

    • Transitory effects

      -> Effects that fail to stand out to the investigator
      • only record through purposeful observation
        • feel
        • smell

    • Relational Details

      • Physical placement of items within the scene

    • Functional Details

      • The operating condition of items in the scene
        • can help prove or disprove specific event questions
        • can aid in defining when things occurred,

  • What is required for good crime scene processing?

    • Knowledge
    • Skills and Tools
    • Methodical Approach
    • Flexibility
    • Coordinated Effort

  • What are the basic objectives of law enforcement? Which one(s) is crime scene processing associated with?

    • crime prevention
    • crime repression
    • regulating Noncriminal Conduct
    • Provision of services
    • Protection of Personal Liberty
      • Crime scene investigators must consistently be professional and object

  • What are the objectives of the initial responder on the scene? What is the FIRST concern?

    • Bring Site under control 
    • coordinate the employment of available resources 
    • document the information provided
    • sure officer safety
    • provide for emergency care
    • secure and control the scene and all those in it
    • release the scene to the appropriate authority

  • What is used to ascertain the perimeter of the crime scene?

    • Primary focal points
    • natural entry and exit points
    • secondary scenes

  • What is the downside to testimonial evidence?

    • People may purposefully lie to investigators or the court
    • Misperceive events and report those misperceptions
    • Unknowingly fill in the blanks in their perceptions

  • What is a crime scene control log and what should be included in it?

    • Need to document anyone who enters and exits
      • who entered, when, why, where

  • What is mitochondrial DNA? Who does it come from? Why do we like it?

    • Present in greater numbers in every cell /Fantastic for hair , bone, degraded biological samples

  • What information can be determined by hair analysis?

    • Species,race, body area, pulled, plucked, cut, length, treatment

  • When can you deny access to EMS?

    • Putrefied body/ decapitation 

  • What are the fingerprint ridge characteristics we discussed?

    • Ridge endings, bifurcations, short ridges, enclosures , ridge dots, deltas, overlap, spurs, bridges

  • What is the evidence linkage triangle?

    • The crime scene investigator must consider each piece of evidence a mechanism for linking the scene the victim or the suspect in some form or fashion

  • Are first responders part of the crime scene investigation team?

    • NO

  • What is the standard of investigation?

    • Asses, Observe, Document, Search, Collect Analyze
    • Investigate to the point of beyond a reasonable doubt; probable cause is not enough

  • How can you determine the side of impact on a pane of glass?

    • 3R Rule: Radial cracks form at a right angle on the reverse side of the force
    • 4R Rule Ridge lines on radial fractures are at right angles to the rear

  • What are common crime scene integrity issues?

    • Addition of materials to scene/ destruction of material at scene/ the movement of material in the scene

  • How do you prevent contamination of trace evidence?

    • Protective clothing must be worn by CS personnel, scientific staff and medicalprosnnel taking part in any aspect of searching.
    • Special purpose rooms should be utilized by crime lab personnel for searching items of evidence
      • air filtration systems are important
      • Everything must be cleaned prior to any examination

  • What information should you gather from persons present at the scene and why?

    • Claims by reporting individuals/ information 

Exam 2 Materials

  • What do you consider when reassessing the security boundaries of a crime scene?

    • Areas of interest/ who is allowed to enter and why/

  • What are the various perimeters of the crime scene? Where should you put the crime scene log(s)?

    • inner scene: actual crime only authorized techs and investigators/ working area: police, equipment, trash evidence collection, Outer area: onlookers media. At every perimeter. 

  • How do you handle politicians and supervisors on the scene?

    • enforce use of standard personal protective measure/ enforce entry logs/ create walking zones for authorized visitors

  • How do you handle altering the crime scene during evidence collection?

    • action cannot be undone part of the collecting process

  • What is the road mapping technique?

    • recognize discrete patterns or defects/ place labels and scales/ overall photographs / close up photographs. 

  • What role does videoing have in crime scene documentation?

    • supplement not full key

  • What are the major problems associated with crime scene photography?

    • identification issues/ orientation issues, confused issues, incomplete documentation issues

  • What are the types of approaches to crime scene teams? When would you use each?

    • area approach: single team handles all activities/ functional approach different teams to different actions 
    • Normal scenes: size of organization determine approach/ complex scenes: more complex more require for functional approach

  • What is the order for crime scene processing and why is it done in this order?

    • Photography, sketching measuring/ searching/ collection of evidence

  • What do you need to do to be sure your photographs are admissible for court?

    • accurately depict evidence and scene/ not distorted, relevant to case

  • What is going back in crime scene processing? When do you do it and why is it important?

    • re doing new steps when finding new evidence as is often the case

  • What should you consider when creating entry and exit points for crime scene access?

    • interfere with scene

  • What are the basic issues involved with assessing the crime scene?

    • biohazard/structural hazard/chemical inhalation hazard/ explosion hazards/biochemical hazards

  • Describe the characteristics of the scales/rulers that should be used for photographing.

    • extend full length of impression, evenly positioned 12 inch scale, non reflective, flat and thin, rigid
  • When can you ignore the processing order and go straight to collection?
    • time sensitive evidence
  • What consideration must be made when observing?
    • mental registration of scene/ non intrusive/ only to observe and not move objects
  • What are the standard search patterns? When should you use each one?
    • circle search; confined scenes not cluttered/ strip or line search; exterior scenes large area, rough terrain / grid search intersect different views same area/ zone search small confined spaces / point to point search; rarely used 
  • What are the parts to documenting the crime scene?
    • written notes/ photographing in situ/ video/ sketching
  • How should you focus your camera to ensure clear images?
    • light, focus, depth of field
Exam 3 Materials
  • How do you collect prints from a fire scene?
    • heat from fire stabilizes latent printed, may darken from soot and smoke, lift with lifting tape
  • What are the types of surfaces? What are examples of each? How should you fingerprint on each?
    • porous-paper, cardboard, untreated wood-dfo/ninhydrin/silvernitre cyanoacrylate
    • nonporous smooth-painted, plastic, glass/ cyanocralyte fuming, powders small particle reagan
    • nonporous rough; vinyl, leather, textured countertops-cyanoacrylate fuming, powders , use silicone based casting material textured surface lifting tape
    • special; skin, tape-adding paper technique, cyanocaruylate fuming, magnetic powder, iodine fuming. 
  • What are the common characteristics of crime scene notes and reports?
    • notes; detailed narrative descriptions of observations and actions taken by the crime scene investigator support sketches & pictures
    • report; a synopzised version of crime notes (intro, characteristics of scene, conditions, environmental, entry exit, scene docs, search for prints, additional examinations, 
  • What is the purpose of the crime scene sketch? What are the essential elements?
    • graphically illustrates the layout, orientation, and interrelationship of the scene and evidence
      • heading/diagram area/ legend/ title block/ scale and direction notations
  • What is the difference between the notes and the report? What information should be put in each?
    • report is summarized version of extensive notes 
  • What is the difference in triangulation between a regular and an irregular shaped object?
    • irregular require two straight line measurements from two distinct landmarks in room to center mass of item. 
    • regular require 4 straight line measurements 
  • How do you measure using triangulation? Rectangular coordinates? Baseline coordinates? Total mapping station? When should you use 
  • each?
    • baseline:used in exterior with limited landmarks, single measurement is made from the evidence to the baseline at a right angle
    • rectangular coordinate: interior scenes with clear boundaries, two measurements made from object to walls at right angle
    • triangulation: evidence measured from center of mass to surrounding walls at right angles two measurements required
    • total station mapping: combines transits, lasers, and computer technology
  • What is the 3-4-5 rule?
    • for any triangle where the sides at right angles to each other are 3 units by 4 units the distance bw tow points is 5 units
  • How do you collect fingerprints that may be examined for DNA?
    • sterile equipment(brush, powder must be new must use non magnetic powder) 
  • How do you mix dental stone for casting?
    • room temp water, potable water, water then add powder slowly and evenly let powder soak for 30 secs hand mix
  • What is the RUVIS?
    • Reflected ultraviolet imaging system, provides enhanced perspective for viewing blood, prints, etc
  • Why do you document failed investigative efforts?
    • negative evidence 
  • What are the standard sketch viewpoints?
    • Cross Projection Sketch/ birds eye view/ elevation sketch/ three dimensional  or perspective sketch
  • Can you lift prints from skin? How?
Exam 4 Materials
  • How can you determine directionality of a blood droplet?
    • scallops, satellite strains, tail, determine direction of impact
  • What is the difference between a contusion, an incision, and a laceration?
    • contusion(bruising); blood escapes into surrounding tissue results in discoloration
    • abrasion( minor damage to the outer layers of skin
    • lacerations( physical tear of the tissue 
  • What are the different types of body decomposition? Which is the most common? What conditions would lead to each?
    • normal putrefacrtio; body breaks down naturally most common bacteria in GI tract break down tissues
    • adipocere; tissue becomes wax like 
    • mummification; tissued dry become leathery 
  • What are the basic premises of bloodstain pattern analysis? Describe each principle.
    • pattern diversity principle; the variations in combo of blood volumes and forces acting on those volumes lead to recognizable clases of patterns
    • the principle of stain shape and vector correlation; the shape of a bloodstain provides indicators as to the direction of deposition as well as the spatial origin of the blood
    • PAB physically altered bloodstain principle; exposed blood will react to environmental conditions ;airflow, temp, humidity, various of surface in predictable manner
  • What are all the mortises? Describe them (general process, etc) What is the benefit of each?
    • Livor Mortis; settling of the blood into small vessels of circulatory system by gravity/ red-purple discoloration of skin, body position will not change; help recognize manipulation of body pattern inconsistent with final position. 
    • rigor mortis; caused by chem reaction of muscles as they break down, stiffening of muscles, occurs in all muscles small muscles first
    • algo mortis; loss of body heat in corpse; vary depends on environment conditions, body fat, 
  • How can you calculate the angle of impact of a bullet or a blood droplet?
    • use pythagorean theorem to calculate angle and inverse sine measure major and minor axis of droplet or bullet hole
    • width/length=N->inverse of sine of N=impact angle 
  • What is the relationship between the shape of the hole/droplet and the angle of impact?

  • What are the 3 areas of ballastics? Describe what they are, who does them, and where.
    • interior/internal ballistics;  function operation of weapon, bullets ejection, gun shot resideueconducted by the forensic firearms examiner crime lab
    • terminal ballistics; forensic pathologist/ path of bullet through body, damage entry and exit wounds forensic firearms examiner, creat gun powder residue standard at different distances
    • exterior/exteranl ballistics;crime scene analyst; path of bullet through scene
  • What is the theory of bloodstain pattern analysis?
    • blood as a fluid responds to forces in a predictable manner
  • Identify/describe the different types of spatter patterns: cast-off, spurt, swipe, wipe, impact, expectorate, pool
    • castoff; linear or curvilinear- parallel follow line think of ants 
    • spurt; large volume elliptical , overlapping irregular 
    • swipe; accumulation of blood on swipe bnoudary, 
    • wipe-displaced blood form original boundary
    • impact-radiate from central point- change in shape of stains further out
    • expectorate;non linear wide range of size, vacuoles air bubble, dilution due to saliva 
    • pool
  • What are the different types of bullet injuries: penetrating, perforating, grazing, etc
    • penetrating; bullet enters but does not exit
    • perforating; bullet enters and exit
    • grazing; bullet skims across the external aspects of the tissue but does not enter body
    • tangential; bullet skims across the body producing a series of shallow wounds that penetrates to the subcutaneous tissue
  • What are the distinguishing characteristics of the different mechanisms of injury?
    • asphyxia; strangulation, smothering, chocking. congestion of facial features, neck injuries, 
    • sharp force trauma stab, incised wound
    • blunt force trauma
    • gunshot trauma
  • How do you verify a defect is from a bullet?
    • generally irregular asymmetrical shape material pushed out from the defect
  • What are the markings associated with gunshot wounds at different distances?
    • contact; muzzle of the weapon is pressed against body soot and gasses entering the wound
    • close contact; stippling around wound
    • intermediate; only stippling appears no soot  or heat
    • indeterminate; distance shot 
  • What is exsanguination?
    • loss of blood 
  • In regards to bullets: What is tumbling? Deflecting?
    • Tumbling;creates distinctive characteristics, eliminates any family to evaluate impact angel
    • deflections; bullet may show angle at which it deflected.