42:30
continuation of discussion in CDIN 2
Segie Lafadchan
Overview
This video details various methods for preserving evidence in criminal investigations, emphasizing techniques that ensure evidence integrity for court presentation. It covers photographic and sketching methods for documentation, the use of 3D models, and the crucial but challenging task of preserving witness testimony. The discussion extends to specialized preservation techniques for different types of evidence, the roles and procedures of SOCO (Scene of the Crime Operation) teams, and the meticulous handling, packaging, and sealing of biological evidence like blood, semen, saliva, and urine. The importance of proper documentation, chain of custody, and laboratory analysis is highlighted throughout.
How was this?
Save this permanently with flashcards, quizzes, and AI chat
Chapters
- Evidence preservation is critical because crime scenes can be compromised by human or environmental factors.
- Photography is a primary and highly useful method for preserving a visual record of the crime scene.
- Sketching provides exact measurements and details of evidence and the crime scene, complementing photographs.
- Rough sketches are created at the scene, while finished sketches are refined for court presentation.
These foundational methods ensure that the original state of the crime scene can be revisited and understood, even after it has been altered or disturbed.
A rough sketch made at the crime scene is later redrawn as a neat, organized finished sketch with legends for court presentation.
- The mannequin method uses 3D models to reconstruct the crime scene, clearly indicating injuries or events.
- Preserving witness memory is challenging because human recall fades over time.
- Documenting witness testimony immediately through recordings or written statements is essential.
- Special methods involve specific treatments for certain evidence types, like using formalin for bodies or sealed containers for blood.
These techniques address the limitations of basic documentation and the fallibility of human memory, offering more robust ways to capture and retain critical information.
Using a 3D mannequin to show the exact location and nature of a wound on a victim's body.
- SOCO (Scene of the Crime Operation) specialists are primarily responsible for evidence collection, handling, and transportation, especially in sensational cases.
- First responders or Investigators on Case (IOC) may collect evidence if it's in danger of being destroyed or contaminated before SOCO arrives.
- Proper handling and documentation are crucial to maintain the chain of custody and ensure evidence admissibility in court.
- All collected evidence must be sent to the crime laboratory for examination.
This section clarifies the roles and responsibilities in evidence collection, emphasizing that proper procedures from the outset are vital to prevent evidence compromise and ensure legal validity.
A first responder collecting a potentially fragile piece of evidence to prevent its contamination before the SOCO team arrives.
- Always use protective gloves and avoid touching evidence directly to prevent contamination.
- Change gloves frequently and use disposable equipment for preliminary tests.
- Avoid coughing or sneezing on evidence; use masks if necessary.
- Biological materials should be packaged in paper, not plastic, to prevent moisture buildup, unless the material is wet and needs to dry.
- Separate packaging is required for different individuals' evidence to avoid mixing.
These guidelines are fundamental to preventing contamination and ensuring the integrity of biological samples, which are highly susceptible to degradation and alteration.
Placing bloody clothing in a paper envelope rather than a plastic bag to allow moisture to escape and prevent mold growth.
- For blood on removable items (like clothing), collect the entire item and package it in paper.
- If blood is wet, package it in plastic temporarily, then open to dry at the station.
- For pools of blood, collect samples using swabs from various locations, storing each in a separate container.
- Blood mixed with water can be collected via multiple swabs or by using a syringe and a test tube with a purple cork.
- Dry blood can be cut out if on a removable surface or collected with a distilled water-moistened swab if not.
Detailed procedures for collecting blood, a common and critical biological evidence type, ensure that samples are properly obtained and preserved regardless of their state or location.
Collecting a blood sample from a large pool on the floor by taking multiple swabs from different spots and placing each swab in its own labeled envelope.
- Semen and saliva on removable materials are collected by taking the entire object and packaging it in paper.
- Moist semen or saliva samples can be collected with swabs, placed in paper, and then an envelope, stored cool and dry.
- Urine samples should be collected in a plastic bottle and refrigerated.
- For drug or alcohol analysis, 20 ml of blood or urine is collected in two separate test tubes and refrigerated.
- Body fluids like mouth swabs, vaginal, anal, or penile samples are collected using swabs, air-dried, and packaged in envelopes.
These methods extend evidence preservation principles to other crucial bodily fluids, ensuring their stability and suitability for laboratory analysis.
Collecting a semen sample from a condom by sealing the condom with a clip, refrigerating it, and sending it to the crime lab.
- DNA typing from living persons can be done via blood (collected by a doctor/nurse), saliva swabs, or pulled hairs with roots.
- DNA from deceased persons is typically collected as blood by a doctor/nurse and refrigerated.
- Acceptable packaging containers include paper bags, clear plastic bags, boxes, Manila envelopes, and glass vials.
- Acceptable seals are tamper-evident tapes; Ziploc bags and staples are not considered secure seals.
- Each package must be marked with agency name, case number, item number, date, time, location found, collector's identifier, and a description of the item.
This section covers the specialized collection for DNA analysis and establishes strict standards for packaging and sealing evidence, which are critical for maintaining its integrity and legal defensibility.
Marking a sealed evidence envelope with the case number, the item description ('bloody t-shirt'), where it was found, and the name of the officer who collected it.
- SOCO is called for sensational crimes (bombings, terrorism, armed robbery) or when victims are high-profile individuals (elected officials, diplomats, celebrities).
- The stages of SOCO processing include preparation, securing the scene, preliminary survey, documentation (photography, sketching), evidence collection, and final survey.
- Biological evidence is any evidence derived from living organisms (human, plant, or animal).
- Examples of biological evidence include hair, tissue, blood, semen, saliva, urine, and stomach contents.
- The proper collection and analysis of physical and biological evidence are paramount for case success in court.
Understanding when and how SOCO teams operate, along with the definition and scope of biological evidence, reinforces the importance of systematic investigation for achieving justice.
A SOCO team being dispatched to a bombing incident due to its sensational nature and the need for specialized crime scene processing.
Key takeaways
- Effective evidence preservation relies on a combination of visual documentation (photos, sketches) and meticulous handling procedures.
- Witness testimony is a fragile form of evidence that must be captured promptly and accurately.
- SOCO teams are essential for processing complex and high-profile crime scenes to ensure evidence integrity.
- Preventing contamination is the primary goal when handling biological evidence, requiring specific protocols for collection, packaging, and storage.
- Proper labeling and sealing of evidence are non-negotiable steps that establish the chain of custody and ensure admissibility in court.
- Different types of biological evidence require tailored collection and preservation methods to maintain their analytical value.
- The success of a criminal case often hinges on the quality and admissibility of the physical and biological evidence collected.
Key terms
Evidence PreservationCrime Scene PhotographyRough SketchFinished SketchMannequin MethodWitness TestimonySOCO (Scene of the Crime Operation)Chain of CustodyBiological EvidenceContaminationPackagingSealingCrime Laboratory
Test your understanding
- What is the primary difference between a rough sketch and a finished sketch in crime scene documentation?
- Why is it important to document witness testimony immediately after an event?
- Under what circumstances would a first responder collect evidence instead of waiting for the SOCO team?
- How does proper packaging of biological evidence, like blood-soaked clothing, prevent contamination and degradation?
- What are the key components that must be included on the marking of an evidence package?
- Why are Ziploc bags and staples considered unacceptable seals for evidence packaging?