the crime scene. locard’s principle dr. edmond locard dr. edmond locard director of the world’s...

The Crime SceneThe Crime Scene

Locard’s PrincipleLocard’s Principle

Dr. Edmond LocardDr. Edmond Locard Director of the world’s first forensic Director of the world’s first forensic

lab in Francelab in France Came up with the idea that when a Came up with the idea that when a

person comes into contact with an person comes into contact with an object or another person, a cross-object or another person, a cross-transfer of physical evidence can transfer of physical evidence can occur.occur.

2 Main Types of Evidence2 Main Types of Evidence

DirectDirect CircumstantialCircumstantial

EvidenceEvidence

Direct evidenceDirect evidence Circumstantial evidenceCircumstantial evidence

Trace evidenceTrace evidence Class evidenceClass evidence Individual evidenceIndividual evidence

Direct EvidenceDirect Evidence

Consists of firsthand Consists of firsthand observationsobservations In court, this evidence involves In court, this evidence involves

testimony by a witness about what testimony by a witness about what that witness personally saw, heard, or that witness personally saw, heard, or did.did.

Examples:Examples: Eyewitness accountsEyewitness accounts Police dashboard videoPolice dashboard video ConfessionsConfessions

Circumstantial EvidenceCircumstantial Evidence

Indirect evidence that can be used to Indirect evidence that can be used to imply fact but does not directly prove imply fact but does not directly prove itit

May provide a link between a crime May provide a link between a crime scene and a suspectscene and a suspect

OnlyOnly suspect and victim actually see suspect and victim actually see it left at crime sceneit left at crime scene

Can be physical or biologicalCan be physical or biological

Circumstantial EvidenceCircumstantial Evidence

Examples:Examples: Finding a suspect’s gun at the site of a Finding a suspect’s gun at the site of a

shootingshooting Biological evidence:Biological evidence:

Body fluids, hair, plant parts, and natural Body fluids, hair, plant parts, and natural fibersfibers

Physical evidence:Physical evidence: Fingerprints, footprints, shoe impressions, Fingerprints, footprints, shoe impressions,

tire impressions, bullets, and tool markstire impressions, bullets, and tool marks

Trace EvidenceTrace Evidence Type of Circumstantial evidenceType of Circumstantial evidence Physical transfer of materialPhysical transfer of material Examples:Examples:

HairHair FingerprintsFingerprints SoilSoil BloodBlood KleenexKleenex FiberFiber GlassGlass Paint chipsPaint chips

Class EvidenceClass Evidence Narrows an identity to a group of Narrows an identity to a group of

persons or thingspersons or things CannotCannot specify a single person specify a single person Only excludes people that do not fit Only excludes people that do not fit

the categorythe category Examples:Examples:

Blood typesBlood types Hair colorHair color Common fibersCommon fibers Shoe printsShoe prints

Individual EvidenceIndividual Evidence

Narrows identity to a single person or Narrows identity to a single person or thingthing

Examples:Examples: DNADNA Complete fingerprints(not partials)Complete fingerprints(not partials) Tool marksTool marks Anything torn or broken and left at the Anything torn or broken and left at the

scenescene

5 S’s of Crime Scene 5 S’s of Crime Scene InvestigationInvestigation

Securing the sceneSecuring the scene Separating the witnessesSeparating the witnesses Scanning the sceneScanning the scene Sketching and photograph the sceneSketching and photograph the scene Searching and collecting of evidenceSearching and collecting of evidence

Securing the SceneSecuring the Scene

The most important job at a crime The most important job at a crime scenescene

Performed by the first officer at the Performed by the first officer at the scene, called the scene, called the first responderfirst responder

Safety of all individuals in first prioritySafety of all individuals in first priority Preservation of evidence is secondPreservation of evidence is second Finally record the sceneFinally record the scene

Separate the witnessesSeparate the witnesses

Separation prevents them talking to Separation prevents them talking to each othereach other

Each witness will be asked about the Each witness will be asked about the crime scene and what they observedcrime scene and what they observed

Scan the SceneScan the Scene

Determine if and where photos Determine if and where photos should be takenshould be taken

Determine if there may be a Determine if there may be a secondary crime scenesecondary crime scene Person killed at a party (primary scene)Person killed at a party (primary scene) Dumped in a lake (secondary scene)Dumped in a lake (secondary scene)

Sketching the SceneSketching the Scene

First is a Rough Sketch done at the sceneFirst is a Rough Sketch done at the scene Must be Must be accurateaccurate and and to scaleto scale Note body, evidence, doorways, windows, Note body, evidence, doorways, windows,

walls, trees, cars, and movable objectswalls, trees, cars, and movable objects Distances should be measured and Distances should be measured and

recordedrecorded Case number, date, location, and time Case number, date, location, and time

should also appear on the sketch should also appear on the sketch

Rough SketchRough Sketch

QuickTime™ and a decompressor

are needed to see this picture.

Final SketchFinal Sketch

Usually done by a computerUsually done by a computer Presented in courtPresented in court

Photographing the Photographing the Crime SceneCrime Scene

Photograph:Photograph: All evidenceAll evidence Doors and Doors and

windowswindows Anything out of Anything out of

the ordinarythe ordinary

Searching and Collecting EvidenceSearching and Collecting Evidence

Must be properly packaged, sealed, and Must be properly packaged, sealed, and labeledlabeled

Dry evidence - placed in a paper bindle, Dry evidence - placed in a paper bindle, put into a plastic bag, sealed with tape, put into a plastic bag, sealed with tape, labeledlabeled

Wet evidence - placed in a paper bag to Wet evidence - placed in a paper bag to allow drying, then treated like dry allow drying, then treated like dry evidenceevidence

When bag is sealed, person must sign When bag is sealed, person must sign their name across the sealtheir name across the seal

Making a paper bindleMaking a paper bindle

Fold the paper into thirds both Fold the paper into thirds both directions so you end up with 9 directions so you end up with 9 rectanglesrectangles

Place your evidence in the middle Place your evidence in the middle and fold paper around itand fold paper around it

Collecting EvidenceCollecting Evidence

Evidence LabelEvidence Label

Chain of CustodyChain of Custody

Must be attached to evidence containerMust be attached to evidence container Starts with person who finds evidenceStarts with person who finds evidence The next person to use or analyze the The next person to use or analyze the

evidence must fill out a labelevidence must fill out a label Ensures evidence is handled correctlyEnsures evidence is handled correctly If it is not handled correctly, can be If it is not handled correctly, can be

traced to who’s responsibletraced to who’s responsible

Crime Scene ReconstructionCrime Scene Reconstruction

Crime scene reconstruction involves: Crime scene reconstruction involves: forming a hypothesisforming a hypothesis of the sequence of events of the sequence of events from before the crime was from before the crime was

committedcommitted

BEWARE of staged crimes (cover BEWARE of staged crimes (cover ups)ups)

Staged Crime ScenesStaged Crime Scenes

When the lab results do not match up with When the lab results do not match up with the testimony of witnesses, it can mean the testimony of witnesses, it can mean the crime was staged; common examples the crime was staged; common examples include: include:

Staging a fire—to cover bankruptcy. Staging a fire—to cover bankruptcy. Staging a suicide—to cover a murder. Staging a suicide—to cover a murder. Staging a burglary—to collect insurance Staging a burglary—to collect insurance

money.money.

Staged Crime ScenesStaged Crime Scenes

To help determine whether a crime To help determine whether a crime scene was staged, consider: scene was staged, consider:

Whether the type of wound found on the Whether the type of wound found on the victim matches the weapon employed. victim matches the weapon employed.

Whether the wound could have been Whether the wound could have been easily self-inflicted. easily self-inflicted.

The mood and actions of the victim before The mood and actions of the victim before the event. the event.

The mood and actions of a suspect before The mood and actions of a suspect before the event.the event.