Comprehensive Study Guide for Criminalistics and Crime Scene Preservation

Fundamentals of Crime Scene Preservation and Criminalistics

The primary objective of crime scene preservation is to guarantee the secure and integral collection of all vestiges present. This fundamental principle ensures that the material integrity of the scene is maintained for forensic analysis, rather than focusing on secondary concerns such as media presence or administrative speed. Within the field of criminalistics, a "vestige" (vestígio) is defined specifically as any material element found at the scene that is related to the investigated fact. It is important to distinguish this from "evidence"; a vestige officially becomes evidence when it is proven to be related to the criminal event through forensic investigation.

The process of maintaining the authenticity and traceability of these materials is known as the Chain of Custody. Its central purpose is to provide a documented history of each piece of evidence to ensure it has not been tampered with or contaminated from the moment of discovery to its presentation in court. This system is vital for the legal validity of the evidence.

Spatial Classification of Crime Scenes

Forensic science classifies crime scenes into distinct areas based on their relationship to the criminal act. The "Immediate Scene" (Local Imediato) is the specific geographic space where the criminal event directly occurred. Surrounding this is the "Mediate Scene" (Local Mediato), which consists of the adjacent areas that possess a possible relationship to the event. Finally, the "Related Scene" (Local Relacionado) refers to any distinct or geographically separate area that is nonetheless linked to the criminal event through the movement of the perpetrator, the victim, or the transportation of vestiges.

Procedural Responsibilities and Scene Isolation

Upon arriving at a crime scene, the very first provision of the police team is to isolate and preserve the area. The first professional responsible for this initial preservation is generally the police officer who arrives first at the scene, rather than the forensic expert or the delegate. The core goal of external isolation is to control the access of unauthorized individuals, as the presence of curious onlookers or unnecessary personnel can lead to the alteration, contamination, or total loss of vestiges. Inadequate isolation is a primary cause of investigative failure because it jeopardizes the purity of the physical evidence.

Strict protocols must be followed regarding the entry of people into the scene. Any unnecessary entry is strictly prohibited as it provokes contamination. Furthermore, the handling ofvestiges must be done with professional care; for instance, any member of the forensic team must use gloves. The primary purpose of wearing gloves is to avoid the contamination of vestiges with the handler's DNA, fingerprints, or other foreign materials.

Technical Documentation and Recording Techniques

A forensic survey and its subsequent documentation must occur before any alteration or cleaning is done to the scene. The expert is required to register all observable aspects, regardless of their perceived relevance at the time, to ensure a complete record. Documentation specifically includes technical photography, which serves to provide a technical record of the location and the vestiges for the court and investigation, rather than for journalistic purposes. This photographic record must be initiated before any manipulation of the vestiges occurs.

Different types of photography are used to capture the scene effectively: panoramic photography is employed to demonstrate a general view of the environment, while detailed technical shots record specific vestiges. In addition to photography, the "peridial sketch" or "croqui" is used. Its specific function is to represent the positions of objects and the distances between them graphically, allowing for an accurate spatial reconstruction of the scene. Furthermore, recording the climatic conditions at the time of the investigation is essential because weather factors can significantly interfere with the conservation of vestiges.

Handling Deceased Persons and Specific Vestige Types

In cases involving a corpse, the body must not be moved or manipulated until authorization is given by the competent forensic authority. The removal of the body only occurs after the forensic examination of the scene is complete. The position of the corpse is a critical piece of data used primarily to analyze the dynamics of the fact (how the event unfolded). Professionals perform a "perinecroscopic examination," which evaluates the circumstances and conditions of the body as it was found at the scene, looking at the immediate surroundings and the state of the victim.

Vestiges are categorized by their nature. "Biological vestiges" include materials such as blood, saliva, and human tissues. "Latent vestiges" are those that are invisible to the naked eye and require specific scientific techniques or chemical reagents to be visualized. Any vestige found on the ground must be preserved and recorded in its original position before collection. Any alteration to the original position of objects at the scene is highly detrimental as it can compromise the reconstruction of the event's dynamics. The ultimate goal of conducting a forensic expert examination at a scene of violent death is to produce technical elements that support the investigation, providing an objective basis for the judicial process.