Crime Scene Investigation & Physical Evidence Processing Flashcards

When photographing a crime scene, the correct documentation sequence is:

Answer: Overall establishing shots first, then mid-range context photos, then close-up detail photographs

The standard approach is to work from general to specific: overall shots establish the scene's spatial context, mid-range shots show relationships between evidence items, and close-up shots capture individual item detail. Reversing this order risks altering the scene before contextual documentation is complete.

Locard's Exchange Principle, foundational to physical evidence forensics, states that:

Answer: Whenever two objects come into contact, there is always a transfer of material between them

Dr. Edmond Locard's principle holds that physical contact between a perpetrator and a scene or victim always results in a mutual transfer of trace materials (hair, fibers, soil, glass fragments, etc.). This underpins the entire logic of physical evidence collection — the perpetrator both leaves traces and takes traces away.

Which type of physical evidence is MOST vulnerable to contamination and degradation if proper collection protocols are not followed?

Answer: Biological evidence such as blood, saliva, and touch DNA

Biological evidence is highly susceptible to contamination from the examiner, environmental conditions (heat, humidity), cross-contamination between items, and DNA degradation from UV light or microbial activity. Strict collection protocols — gloves, separate packaging, refrigeration — are critical to maintain evidentiary value.

The primary purpose of establishing a defined crime scene perimeter as the first responding action is to:

Answer: Prevent unauthorized access and protect the integrity of physical evidence from disturbance or contamination

The moment a crime scene is disturbed — by responders, bystanders, or the environment — evidence may be destroyed or contaminated. Establishing a perimeter is the first protective action to preserve the scene in its original state before any systematic documentation or collection begins.

When multiple items of physical evidence are collected from the same crime scene, each item should be:

Answer: Packaged separately with individual labels documenting location, date, time, and collector

Each item must be individually packaged and labeled to prevent cross-contamination between items and to maintain a clear, traceable chain of custody. Combining items in a single container can destroy trace evidence, introduce contaminants, and create evidentiary challenges that may render items inadmissible.

A forensic examiner arrives at a scene where a deceased victim is present and there is a strong odor suggesting decomposition. The FIRST action the examiner should take is:

Answer: Don appropriate personal protective equipment (PPE) before entering the scene

Personal safety is always the first priority. Biological hazards at decomposition scenes include pathogens, toxic gases, and biohazardous materials. No evidence collection activity should begin before the examiner is properly protected with appropriate PPE (gloves, respirator, Tyvek suit as needed) to prevent both self-contamination and scene contamination.