Forensic Techniques and Tools

From: inteligencialtda

Forensic investigations, as highlighted by experts Leonardo Kanashiro (the “Cane”) and Ricardo Averbach (Rick Silverback), involve a range of specialized techniques and tools that differ significantly from their portrayal in popular media [00:01:37]. These processes are in constant evolution, with experts continuously learning new methods and technologies [01:04:27].

Role of Forensic Experts

Forensic experts are integral to crime scene investigation and solving crimes. They conduct examinations at crime scenes, analyze traces, and produce expert reports based solely on scientifically proven facts [01:16:29]. They work closely with forensic doctors and investigative police teams [00:39:10]. In São Paulo, forensic teams are highly specialized; for example, some experts focus solely on homicide sites of unknown authorship, while others specialize in engineering-related cases like fires, traffic accidents, or crimes against property [00:20:47].

Key Forensic Tools and Techniques

Luminol

Luminol is a chemical compound used to detect trace amounts of blood and other substances at a crime scene [00:04:35].

• Composition & Application: It consists of a powder mixed with a solution, primarily hydrogen peroxide, inside a spray bottle [00:05:18]. The solution is sprayed onto surfaces [00:05:50].
• Reaction: Luminol reacts with the iron found in hemoglobin in blood [00:08:01], producing a distinct blue glow in the dark [00:06:14].
• Limitations: While it reacts with blood, it can also react with other iron-containing substances like rust, making a positive luminol test a preliminary indicator rather than conclusive proof of blood [00:08:08].
• Purpose: Primarily used to detect “latent blood” (blood that has been cleaned or is invisible to the naked eye) [00:09:39]. Even after cleaning with products like bleach, blood can still be detected on various surfaces, though smooth surfaces are easier to clean [00:10:34].

Feca-Cult Test (Immunochromatographic Test)

After a luminol reaction, a secondary test is often performed to confirm if the detected substance is human blood [00:06:42].

• Function: This rapid test, similar to a pregnancy test, uses a sample collected from the reacted area [01:11:07].
• Mechanism: It reacts specifically with human blood protein, differentiating it from animal blood [00:07:45].
• Origin: The specific test mentioned, “FOB” or Feca-Cult, was originally designed to detect blood in stool, but proved highly useful for forensic science [01:12:02].

DNA Collection and Analysis

DNA is a powerful tool for human identification, as each person’s DNA is unique (with rare exceptions like chimerism) [01:16:16].

• Collection: DNA can be collected from various sources, including blood, hair bulbs, skin cells (epithelial cells), saliva, and even bodily fluids like seminal fluid [00:38:05]. Tools like sterile cotton swabs moistened with distilled water or saline solution are used for collection [01:13:03].
• Locard’s Principle: Every contact leaves a trace, meaning every touch leaves behind genetic material [01:00:09]. This makes DNA a highly effective investigative tool [01:00:09].
• Database Matching: Collected DNA profiles are compared against databases. If a suspect’s DNA is in the system (e.g., from prior convictions or voluntary samples), a match can be made [01:16:16].
• Gender Identification: DNA analysis can also determine the sex of the individual from whom the sample originated [01:16:16].
• Challenges: While powerful, obtaining a DNA sample from a suspect can be difficult due to legal refusal rights, often requiring judicial authorization [00:50:08].

Fingerprint Analysis

Fingerprints are another unique identifier for individuals [00:54:16].

• Collection: Depending on the surface, different powders (e.g., magnetic powder) are used to visualize fingerprints [00:53:17]. These can then be lifted using tape or photographed [00:54:41].
• Databases: Fingerprint databases are generally more comprehensive than DNA databases, making identification potentially faster [00:55:21]. Modern identification cards (RG) are often digitized with fingerprints, linking them to a national database [00:55:38].
• Role of Fingerprint Experts: Specialized experts (Papiloscopists) perform this critical work [00:53:53].

Perinecroscopic Examination

This involves the external examination of a corpse at the crime scene [01:14:39].

• Purpose: Experts analyze the body and all available traces in its immediate surroundings to determine the cause and circumstances of death without internal examination [01:15:06].
• Procedure: This may involve cutting clothes to identify injuries, photographing the scene and the body from various angles, and collecting samples [01:15:27].

3D Scanner

Advanced technology used to create a highly accurate digital reproduction of a crime scene [01:04:51].

• Function: The scanner projects laser beams across the scene (360 degrees), capturing millions of microdots to create a precise three-dimensional virtual environment [01:05:02].
• Benefits: Allows for reliable measurements, analysis of distances, and the reproduction of the scene in a virtual space, aiding in trajectory analysis (e.g., bullet paths) and reconstruction [01:05:29].

Forensic Investigation Processes

Crime Scene Protocol

Upon arrival at a crime scene, strict protocols are followed to preserve evidence and prevent contamination [01:08:08].

• Photography: Thousands of digital photographs are taken from every angle before anything is touched or moved, as the scene will never be the same after expert intervention [01:08:49].
• Evidence Collection: All potential evidence, from bloodstains to genetic material (even from knots on bags), is meticulously collected, often using sterile tools and individually wrapped [01:09:31].
• Contamination Prevention: Experts wear gloves and other protective gear, and even their own DNA is cataloged to prevent misidentification due to accidental contamination [01:10:47].

Report Writing

Expert reports are formal documents detailing the scientific findings and conclusions drawn from the investigation [01:16:07].

• Objectivity: Reports must be objective, containing only scientifically proven facts, without assumptions or personal opinions [01:16:26].
• Hypotheses: Experts work by formulating and testing hypotheses, aiming to eliminate unlikely scenarios to arrive at the most probable conclusion [01:14:31].
• Collaboration: Communication between criminal experts and forensic doctors is crucial, especially for cases requiring autopsy for a complete understanding of injuries [00:39:27].

Case Studies and Insights

Charred Body Case

A case involving a charred body in a fire initially appeared to be an accidental death, but forensic analysis revealed a homicide [01:18:48].

• Discovery: A woman’s body was found carbonized inside a burned house [01:19:00].
• Initial Observations: The light box was intact, suggesting the fire wasn’t accidental (e.g., short circuit) [02:35:05]. The fire’s focus was on the sofa where the victim was found [02:03:09].
• Traces: Blood drops were found leading from the gate to inside the house, and another trail led outwards [02:06:05]. The pattern of blood drops can indicate movement [02:07:06].
• Child’s Safety: A child was found unharmed in a room with a closed door and a wet towel at the bottom, suggesting deliberate protection from the fire [02:09:47].
• Autopsy Findings: The forensic doctor discovered multiple stab wounds (abdomen, chest, neck) that caused her death, not the fire [02:40:04].
• Resolution: The victim’s ex-partner confessed to stabbing her during an argument, then setting the house on fire to conceal the murder [02:40:26]. He protected his daughter by putting her in a room and sealing the door before fleeing [02:41:42]. DNA analysis confirmed the presence of both the victim’s and the man’s blood at the scene [02:45:29].

Dismembered Body Case

Forensic experts investigated a case where a woman’s dismembered body parts were found in garbage bags [02:44:48].

• Discovery: Garbage collectors found a severed hand with painted nails, then further body parts in other bags [02:48:19].
• Initial Findings: The cuts were very straight, indicating a sharp instrument was used [02:48:06]. DNA analysis confirmed both halves belonged to the same woman [02:58:29].
• Investigation: DNA was collected from the knots of the bags, and also from a knife and saw found at the suspect’s house [02:58:36].
• Resolution: The suspect confessed to strangling his girlfriend during an argument (fueled by cocaine use) [03:00:03], then dismembering her body to dispose of it [03:00:03]. His DNA matched the samples from the scene [02:58:49].

Rape and Homicide Case

A case of rape followed by homicide highlighted the importance of DNA collection from the victim’s body [03:18:47].

• DNA Success: DNA was successfully collected directly from the victim’s body (clothes, hands, neck), leading to the identification of the perpetrator [03:20:03].
• Serial Offender: This individual was later linked to multiple other unsolved rape cases through DNA matches in a database maintained by hospitals that care for victims of sexual violence [03:24:54].

Herbie Beetle Car Case (Feminicide)

A unique vehicle helped solve a feminicide [03:39:35].

• Investigation: A woman was shot dead on the street [03:46:14]. Surveillance cameras showed the perpetrator fleeing in a distinctive car, a Beetle painted to resemble “Herbie” [03:39:35].
• Identification: The unusual car led police to intercept the suspect, who was the victim’s husband [03:39:35]. He confessed to ordering her killing [03:39:35].

Nike Shoe Print Case (Fratricide)

A distinct shoe print provided crucial evidence in a fratricide [03:40:07].

• Scene: A man was found dead, and a clear Nike shoe print was found in blood on the floor [03:40:07].
• Suspect: The victim’s cousin, who lived next door, was a suspect due to a history of fights [03:40:07].
• Resolution: Police found the specific Nike sneakers, still wet from cleaning, at the cousin’s house [03:40:07]. Confronted with this, the cousin confessed to killing his relative during a fight [03:40:07].

Challenges in Forensic Investigation

• Public Perception: The trivialization of violence and the dramatization of crime in media can distort public understanding of forensic work. People may doubt scientifically proven facts or idealize criminals [03:11:42].
• Complexity of Cases: Crime scenes are unique and unpredictable. The lack of visible traces or misleading information from witnesses can add layers of difficulty [03:11:42].
• Human Element: Despite scientific advancements, the human element remains vital. Experience and logical reasoning are key for experts to establish good hypotheses and recognize patterns [02:19:35].
• Emotional Toll: Forensic work, particularly in homicide investigations, can be emotionally taxing, requiring professionals to maintain objectivity while confronting horrific scenes [03:22:04]. However, this exposure often deepens appreciation for life and human relationships [03:26:01].
• Legislation and Impunity: Laws regarding criminal execution and sentencing (e.g., early release from prison) can contribute to a sense of impunity, as criminals may calculate that the risks outweigh the rewards [03:07:07]. The ease of access to illegal weapons also poses a significant challenge [03:19:04].

Future of Forensic Science

Forensic science is constantly evolving. Newer technologies like 3D scanners are enhancing crime scene documentation and analysis [01:04:51]. The continuous accumulation and sharing of knowledge and experience among experts are vital for progress [03:35:36].