Slide 1

CRIME SCENE INVESTIGATIONGoal of Crime InvestigationFind the guilty party.Exonerate the innocent.If the investigator doesnt preserve the evidence or document that preservation correctly, the evidence isnt useful in court.Crime Laboratory cant make the evidence make sense if it isnt collected correctlyTwo Evidence TypesTestimonial evidence is given in the form of a statement under oath in response to questioning.Physical evidence is anything used, left, removed, altered or contaminated during the commission of the crime, by either the victim(s) or suspect(s).Physical EvidenceCannot lie, forget, be mistaken when properly identified, collected and preserved.Is demonstrable.Is not dependent on the presence of witnesses.Is, in some instances, the only way to establish the elements of the crime.Two Types of Physical EvidenceIndividual Characteristics. A piece of evidence that is unique and can be identified to the exclusion of all others. Fingerprints DNAClass Characteristics Features shared by all members of a group or class FootprintsApproach.Render medical aid.Identify additional victims or witnesses.Secure the scene and physical evidence.Notifications made appropriately.ApproachDrive carefully Sirens and high speed can be risky.Scan for suspicious things or persons.Be alert to evidence, witnesses and victims.Call for more help and dont dismiss the helpuntil the situation is clear.Rendering Medical AidThe most important issue is to save a human life or prevent additional injury.If the crime scene becomes contaminated while rendering aid, that is a price that must be paid.There arent hard and fast rules that can be applied discretion must be used.Identifying Witnesses/VictimsMay need medical attention.Witnesses identify suspects and locations of additional evidence.Separate the witnesses so they dont cross contaminate stories.Be observant if witnesses give identical stories they may have collaborated before police arrived.Secure the SceneEstablish a perimeter. Yellow tape. Barriers. Close the door for indoor crimes. Police officers.Secure scene and evidence. Check for exit strategy of the criminal and follow to check for additional evidence.Secure the SceneCrime Scene Log is used to document the investigation: Who entered the scene Who left the scene Time In and Out Reason for entry to the sceneKeep out unauthorized police or fire personnel.Make NotificationsFirst Responders notify superiors.Call in Crime Scene Specialists: Photo Specialists Medical Examiners Crime Scene UnitsTypes of ScenesMajor Scenes Homicides Officer involved shootings Felonious assaults in which death could occur. Cases with potential for a major investigationNonmajor or discretionaryMajor Indoor Scenes: Observations and NotesTimeEntrances and Exits DoorsOpenClosedLockedType of lock (e.g. deadbolt)Forced WindowsOpenClosedLockedUnlocked Lights (on/off) OdorsCigarettes, cigars, perfume, alcohol, gas, gun powder, unusual odors.Names of Persons at the scene, including emergency personnel.Condition of the scene: In disarray/good order Furniture tossed about Stains Position of weaponsAvoid the following: Do not touch inside doors, doors and door frames. Do not move anything. Do not smoke, or use , the telephone, toilet, sink or ashtrays. Beware where you stand and what you touch.Hold your hand behind your back while surveying the crime scene.Outdoor Crime ScenesEstablish and protect a large perimeter, especially at parks, beaches or open areas.If tire/footprint or other impression evidence is found, warn others to stay away.Try to determine the suspects route of approach and escape.Identify and protect evidence, then collect it. Some evidence is difficult to collect.Secondary Crime ScenesEvidence may be located some distance from the original crime scene: Discarded clothing Discarded weapons Blood trailsProtect secondary crime scene evidence as well as primary crime scenes.Death CasesFour methods by which death can occur: Natural Causes Accidental Death Suicide HomicideMedical Examiner makes this decision.Death CasesAll death scenes should be treated like a homicide until the medical examiner declares otherwise.First responders should not hesitate to ask for assistance if needed. Better to err on the side of caution.Key to a successful investigation is documentation.Death Cases

Make note of some of the following: Believability of the witnesses.Jittery, nervous, anxious to leave the scene?Does their version of the incident seem questionable? Condition of the scene. History of the victim and/or suspect if known. Preservation of notes or writing for later analysis. Preserve medications and containers.Documenting the Crime Scene

Investigators have only a limited amount of time to work a crime site in its untouched state.Photographs, notes and diagrams document the condition of the crime site and to delineate the location of physical evidence.Photographs, notes and diagrams prove useful during the subsequent investigation AND are also required for presentation at a trial often months or years later.Documenting the Crime Scene

A lead investigator will start the process of evaluating the area before collecting evidence. First, the boundaries of the scene must be determined. This is followed by the establishment of the perpetratorspath of entry and exit. The investigator then proceeds with an initial walkthrough of the scene to gain an overview of the situation and develop a strategy for the systematic examination and documentation of the entire crime scene.Crime Scene Search The crime scenecoordinator may choosefrom a variety of crimescene search patternsbased upon the type andsize of the crime scene. Key is to be orderly andthorough- dont walkover too much but dontmiss anything.

The Search The search for physical evidence at a crimescene must be thorough and systematic. The search pattern selected will normallydepend on the size and locale of the sceneand the number of evidence collectors. Physical evidence can be anything frommassive objects to microscopic traces.Collecting Physical Evidence Although much physical evidence is clearly visible,some may only be detected at the crime laboratory. E.g. Semen on sheets after a sexual assault. It is important to notice and collect possible carriersof trace evidence, such as clothing, vacuumsweepings, and fingernail scrapings, in addition tomore obvious physical evidence. Investigators need to keep from contaminating theevidence e.g. their DNA or fibers.The Victim Can Provide Evidence The search for physical evidence must continue tothe autopsy room of a deceased victim. The medical examiner or coroner will carefullyexamine the victim to establish a cause and mannerof death. Tissues and organs will be retained for pathologicaland toxicological examination. Also they will provide any physical evidence from thebody of the victim.Beyond The Crime SceneThe following are often collected and sent to theforensic laboratory:1. Victims clothing2. Fingernail scrapings3. Head and pubic hairs4. Blood (for DNA typing purposes)5. Vaginal, anal, and oral swabs (in sex related crimes)6. Recovered bullets from the body7. Hand swabs from shooting victims (for gunshot residueanalysis)Collecting and Packaging Evidence Forceps and similar tools may have to be used to pickup small items. Unbreakable plastic pill bottles with pressure lids areexcellent containers for hairs, glass, fibers, and otherkinds of trace evidence. Manila envelopes, screwcap glass vials, or cardboardpillboxes are also good containers Ordinary mailing envelopes should not be usedbecause powders will leak out of their corners.Packaging to Preserve Evidence Each item or similar items collected at differentlocations must be placed in separate containers. Packaging evidence separately prevents damagethrough contact and prevents crosscontamination. The wellprepared evidence collector will have alarge assortment of packaging materials and toolsready to encounter any type of situation.Packaging Trace evidence can also be packaged in a carefullyfolded paper, using a druggist fold. Two frequent finds at crime scenes warrant specialattention. If bloodstained materials are stored in airtight containers,the accumulation of moisture may encourage the growthof mold, which can destroy the evidential value of blood. In these instances, wrapping paper, manila envelopes, orpaper bags are recommended.Obtaining Reference Samples Standard/Reference SamplePhysical evidence whose originis known, such as blood or hair from a suspect, that can becompared to crimescene evidence. The examination of evidence, whether it is soil, blood, glass,hair, fibers, and so on, often requires comparison with aknown standard/reference sample. Although most investigators have little difficulty recognizingand collecting relevant crimescene evidence, few seemaware of the necessity and importance of providing the crimelab with a thorough sampling of standard/reference materials.Evidence Recovery Log A chronological record of who found whatevidence, where, witnessed by whom, andnotations about other ways the evidence mayhave been documented, e.g., photography