Crime Scene Investigation CSI

By: Dr/ Marwa Magdy Demonstrator of forensic medicine & toxicology

Expectations

Objectives

• Vocabulary• principles of crime scene investigation• Stages of CSISecuring SearchingDocumentingCollecting & preserving trace evidence

Crime scene: Any physical location in which a crime or accident has occurred suspected of having occurred.

Source: http://www3.sc.maricopa.edu/ajs/crime_scene_technician.htm

Physical evidence: any material items that would be present at the crime scene, on the victim, or found in a suspect’s possession.

Trace evidence: physical evidence present at the crime scene in small but measurable amounts.

Suspect: person thought to be capable of comitting a crime.

Vocabulary

1) Time frame

2) Crime scene zone

3) Crime scene investigation team

4) Crime scene investigation equipment

5) Crime scene search patterns

Source: http://www3.sc.maricopa.edu/ajs/crime_scene_technician.htm

Principles of CSI

Time frame• Arrival of the CSI team should be as soon as

possible since the crime was reported.

• Late arrival at the crime scene may result in loosing important evidence.

Crime scene zone

• Boundaries of the crime scene → as far as signs of committing a crime are visible.

Boundaries are defined by the head of the CSI team.

• Assailant’s path of entry andexite.g: windows,doors.

CSI Team

• Head of the crime scene investiagtion team “prosecutor” . النيابة وكيل

• Forensic pathologist الشرعى الطبيب• police officer (investigator)المحقق • Photographer الجنائى المصور• Latent prints expert البصمات خبير• Explosives expert المفرقعات خبير• Members of CSI team الجنائى البحث فريق أعضاء

CSI equipments• equipment for securing and preserving the crime

scene• equipment for collecting and packaging of evidence

• equipment for recording the crime scene and evidence.

Tools for evidence collection• Rubber gloves.• Strong flashlight.• Syringes & needles.• Forceps & scissors .• Hand lens.• Labels & containers.• Plastic vials & jars.• Paper bags.

Searching the crime scene

Stages of CSI

1. Securing the crime scene2. Searching the crime scene3. Documenting & photographing4. Collecting & preserving evidence

Securing the scene• Defining boundaries of the crime scene

• Entry is prohibited

• Every person who enters the crime scene has the potential to destroy physical evidence.

• Ensuring security for the crime scene investigation team members

• CSI team should wear protective clothes.

CSI video 2.flv

Searching the scene

Crime scene search patterns

• Many distinctive methods of searching the

crime scene.

• For different types of crimes, different search

patterns are suggested.

Searching the crime scene

Documenting the scene

• 3 methods of crime-scene recording:

• Photography • Sketches • Notes

• Ideally all 3 should be used.

Photography • At this stage touching or moving objects is

prohibitted

• Particularly cadavers SHOULD remain untouched

• Objects may be marked with numbers and photographed

• what ?Crime scene & adjacent areasEntry & exitCadaver , weapon & injuries

Pictures can tell …

sketches

Collecting & preserving evidence

• Common types of trace evidenceBloodSemenSalivaFingerprintsHairsFibersExplosivesWeapons

Glass ImpressionsPaintPetroleum productsPlastic bagsPowder residueSoil and mineralsTool marksWood

Why is trace evidence useful?

Blood stain

Finding The Stains:

Reagents :“Luminol and fluorescein” can reveal blood that has been watered down to a ratio of 12000:1.

Seminal stain

• Seminal stains on dark material often have a white glistening appearance.

• Preliminary test (Ultraviolet light): bluish white fluorescence.

• Confirmatory test (Microscopic detection of spermatozoa)

• DNA of assailant

Saliva stains

• Could be detected anywhere on clothing,bites,enveloppe& cigarette bits.

• DNA of the assailant

Hair Human or animal Race Origin Manner in which hair

was removed Drugs ingested DNA analysis

Latent prints

• Types :FingerprintPalmSole LipEarFoottyre

Latent prints