Crime Scene Investigation Lecture Notes

Crime Scene Reconstruction

• The major purpose of physical evidence is crime scene reconstruction.

Evidence Collection

• Gunshot residue: If a gunshot residue test cannot be completed, use a paper brown bag tied with tape to protect residue on hands.
• Deceased body: Place the body on a clean white sheet before putting it in a body bag.
• Sexual assault evidence: Three major sources are the victim, suspect, and crime scene.
• Tire and footwear impression: Proper collection requires taking a photo and making a cast.
• Blood samples from the deceased: Collect from the heart and any major blood vessel.
• Weapons found in water: Keep the weapons in the same water.
• Clothes from sexual assault victims: Carefully secure in a paper bag due to potential transfer evidence.

Sexual Assault Cases

• Physical evidence can identify or exonerate a suspect.
• Common defenses: Consent and misidentification are the two most common defenses used by a suspect in a sexual assault case.

Homicide Investigations

• Close-up photos of each wound should be taken with and without flash.
• Crime scene analysis: Helps determine if a death is a suicide, accident, or homicide.

Bloodstain Evidence

• Proper documentation is the primary focus for the crime scene investigator.
• Collection: Collect blood stains on clothes by taking the whole garment.

DUI Investigations

• Consent is needed to take blood from a DUI suspect.
• If consent is denied, obtain a warrant from a municipal court judge.
• Waiting Period: Officers must wait a minimum of 20 minutes before administering an alcohol test to allow raw alcohol to dissipate from the mouth.

Firearm Evidence

• Class characteristics of bullets: Identified by examining twists, bores, and grooves.
• Gunshot residue (GSR): May be found on the cheek and hand of a suspected shooter after using a rifle or shotgun.
• Rifling: Consists of lands and grooves within the firearm barrel.

Crime Scene Investigation Principles

• First step in reconstruction: Recognize physical evidence after securing the scene.
• Low Carb Principle: Transfer of energy = Secondary trace of evidence. Evidence can be transferred multiple times.
• Linkage Triangle: Transfer of evidence between the suspect, the victim, and the scene.
• Evidence Admissibility: Must be legally obtained, ethical, and scientific to be admissible in court.
• First responder duties: Remove and detain suspects and victims.
• Crime Scene Sketches: Provide factual data for crime scene reconstructions (based on observations).

Fingerprint Evidence

• Latent fingerprints: Must be developed with powder.
• Natural fingerprints: Cotton or synthetic fingerprints are manmade
• Patent Fingerprints: Visible to the naked eye.
• Contamination: Can occur during laboratory processes on latent fingerprints.
• Fingerprints are checked on the NCICS. Only those of individuals 14 years of age or older can be fingerprinted.

General Evidence Principles

• Value of physical evidence: Must be recognized, collected, and preserved to be of value.
• Direct evidence: Proves a fact directly.
• Testimonial evidence: Given by a lawyer expert witness; credibility is key.

Impression Evidence

• Common Impressions: Footwear, tire thread, bite marks, and tool marks;
• Tread: Often what makes the print unique.
• Collection: Photograph, measure, and cast the imprints.

Medical Procedures

• Blood Sample Collection: Requires consent; if denied, a municipal court judge can give consent.
• Packaging: Blood taken for alcohol evidence is packaged in glass vials.
• Wound Handling: Should not be touched during autopsy.

Document Examination

• Uttering: The passing off of false documents.

Legal and Ethical Considerations

• Astringent Circumstances: Taking specific items that help identify someone without a warrant.

Traffic Accident Investigation

• Yaw Mark: Tire is on its side.
• Skid Mark: Tire breaks.

Crime Scene Procedures

• Systematic Searches: Crime scene investigators should plan a systematic method for their searches.
• Hair Evidence: The overall examination of hair evidence has been revolutionized due to the development of DNA analysis.
• Projectiles: Projectiles fired from a certain weapon have lands and grooves engrained, this can help the investigator figure out what weapon was used.

Photography and Sketching

• Advantages of Photography: Provides a detailed view of the crime scene; approximates how first responders see the scene.
• Measuring and Sketching: Essential activities at a crime scene.
• Photograph Quantity: It is good policy to take more photographs than fewer photographs.
• Prioritization: Any patent impressions, prints, or trace evidence should be photographed first.

Legal Considerations

• Exclusionary Rule

Arson Evidence

• Packaging: Arson evidence with suspected accelerant should be placed in steel cans, lids, or airtight glass jars.
• Physical evidence can be present at an arson crime scene.

Glass Evidence

• Matching: When glass is broken, the edges can be matched.

Crime Scene Management

• Perimeter: Should be limited to a minimized size.
• Search Methods: The grid method is a better method than the spiral method.

Fiber Evidence

• Fibers collected for a carpet should One main objective of crime scene photography is to;
• Paint specimens on garment should be collected by taking parts of the garment not to lose it. False

General Reminders

• Witness Perspective: At a motor vehicle crime scene, a witness's point of view in relation to events that took place should be illustrated.
• 3 C's of crime scene investigation : Cooperation, Coordination, and Collection.
• Field sketches should be disregarded as evidence (False).
• Take a picture of bullet holes in a wall and measure. And cutting it out of a wall.