2 Processing the Crime Scene Forensic Science begins at the crime sceneInvestigators must recognize physical evidence, collect the evidence, and properly store and preserve the evidencePhysical Evidence – any and all objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator
3 Processing a Crime Scene Secure and isolate the crime sceneRecord the sceneConduct a systemic search for evidenceCollect and package physical evidenceMaintain a chain of custodyObtain standard/reference samplesSubmit evidence to the laboratory
4 Secure and Isolate the Crime Scene Responsibility of first officer to arrive on the scene of a crime to preserve and protect the area to the greatest extent possibleFirst priority is to obtain medical assistance and arrest perpetratorNext, efforts should be made to exclude all unauthorized personnel and isolate area; every person that enters the scene has potential to destroy evidenceDetermine boundaries and establish the perpetrator’s path of entry and exit; crime scene size will depend of locale of scene, size of area, and victims and suspects
5 Record the SceneThere is a limited amount of time to permanently record the crime scene in its untouched stateRecording the scene is necessary to present in trial and delineate the location of evidenceThree methods of recording a crime scene:PhotographySketchesNotes
6 Record the Crime Scene Photography Unless there are injured parties, objects must nor be moved until they have been photographed from all angles. If objects are moved, photographs may not be admissible in court – unless recorded in notes.Items to be photographed:Area in which the crime took place and all adjacent areasPoints of entry and exit from various anglesIf indoors, the entire room and wall area as well as adjacent roomsA body’s position and close up depicting injuries and near by weapons; once the body is removed, the area under the body should be photographedPhysical evidence position and location as well close up (a ruler or other measuring devise may be used as a point of reference)Videotaping with sound is also a popular method of recording a crime scene
7 Record the Scene Sketches Rough sketch of the dimensions of the scene showing the location of al objectsThe dimensions of objects in the sketch are determined by two fixed point – usually the walls of the roomFinished sketches are usually completed with drafting tools (CAD)
9 Record the SceneNotesDetailed written description of the scene with location of items of physical evidenceTime of discovery of evidence, by whom, how and by whom it was packaged and marked, and the disposition of the item after it was collectedNotes may be the only written record to refresh the memory of the investigatorsTape-recording is commonly done
10 Conduct a Systematic Search for Evidence Searching the crime scene depends on locale and size of area as well as victims and suspectsLead investigator will subdivide the scene into segments a search each segment individually or the search may start at some outer point and gradually move toward the center of the scene in a circular fashion
11 Conduct a Systematic Search for Evidence Areas searched must include all probable points of entry and exitSearch for evidence will depend on type of crime:HomicideBurglaryVehicularKidnappingPhysical evidence can be anything from massive objects to microscopic tracesSome objects may only be traceable in laboratory settings therefore the collection of possible carriers of trace evidence is importantMinute traces of blood on clothingHair or fibers in vacuum sweepings
12 Conduct a Systematic Search The search for evidence continues in the autopsy of a deceased victimMedical examiner will determine cause and manner of death and will retain tissues and organs for toxicological and pathological testingThe following should be collected and sent to the forensic lab:Victim’s clothingFingernail scrapingsHead and pubic hairBloodVaginal, anal and oral swabs (in sex related crimes)Recovered bullets from the bodyHand swabs from shooting victims (gunshot residue)Virtual Autopsy
13 Collect and Package Physical Evidence Physical evidence must be handled and processed in a way that prevents any change from the crime scene and the time it is received by the crime laboratoryChanges arise through contamination, breakage, evaporation, accidental scratching or bending, or loss through improper or careless packagingWhenever possible, evidence should be submitted to the lab intact; blood, hairs, fibers, soil particles should not be removed from articlesEach different item or similar items collected at different locations must be placed in separate containers to prevent damage and cross-contamination.
14 Examples of packaging containers and techniques: Plastic pill bottles for hairs, glass, fibers, and other types of small evidenceManila envelopes or screw-top glass vials for trace evidence (never ordinary envelopes because of possible leaking)To avoid accumulation of moisture and mold, bloodstained materials should be packaged in manila envelopes or paper bagsClothing should be air dried and placed in paper bags to allow air flowCharred debris should be sealed in an airtight container to prevent evaporationSee Appendix I for proper collection and packaging techniques
15 Maintain Chain of Custody Chain of custody – continuity of possession must be established whenever evidence is presented in courtStandard procedures includeRecording the location of the evidenceMarking it for id (collector’s initials and date)Properly completing evidence submission forms for lab analysisAccounting for every person that handles or examines the evidence.
16 Obtain Standard/Reference Sample Examination often requires comparison with a known standard or reference sampleHit and Run might require paint sample from car to compare to paint at sceneBloodstained evidence must be compared to blood samples or buccal swaps from all people at the crime sceneEvidence may also be compared to substrate controls – materials adjacent to or close to areas where the evidence has been depositedIf a burned area is suspected to be covered in gasoline, it should be compared to a similar area not suspectedBloodstains on garments should be compared to area without stains
17 Submit Evidence to the Laboratory Evidence is submitted by personal delivery or mail shipment depending on the location of the labEvidence submission forms should be completed which provides a brief history of the case, the evidence submitted, and the type of analysis that should be preformedAnalyst not strictly bound to specific test requested if new evidence is found or to search for trace evidence
18 Crime-Scene SafetyBecause of the presence of biological substances with unknown pathogens, care should be taken to avoid contamination and infectionGuidelines set by the International Association for Identification Safety Committee include:Wear protective gloves, shoe covers, liquid repellent coverallsMask/respirators, goggles, or face shieldsEvidence possibly containing body fluids should be labeled as biohazard
19 Legal Considerations at the Crime Scene The removal of any evidence from a person or from the scene of crime must be done in conformity with the Fourth Amendment – the right against unreasonable searchesThere are cases when police can justify a search without warrant
20 Legal Considerations Mincey v. Arizona Undercover police officer, attempting to buy drugs, forced entry into the apartment and was killedWithout a search warrant, police searched the apartment for four days recovering bullets, drugs, and paraphernalia.Evidence was submitted into trial but since it was illegally seized the court could not convict Mincey
21 Legal Considerations Michigan v. Tyler Loren Tyler and his business partner burned down leased propertyFire officials and police officers searched the premises after the smoke cleared, then 4 days,7 days, and 25 days later to collect evidenceTyler and partner were convicted but it was overturned as searches were made without warrants (only initial evidence collected at first search was allowed)
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