Primary Crime Scene:
When first arriving at the scene, the investigator must first determine if the body is at the primary scene or a secondary scene. This can be done through the examination of physical evidence, enabling investigators to determine if the patterns seen are consistent with the actual crime taking place at that very location.
For example, if wounds on the body are traumas consistent with copious blood flow but the body has no pooling around it, the body may have been taken to a secondary spot after the initial assault.
Patterns can reveal if the deceased was murdered in one location and transported to another in order to delay or prevent discovery; this then is considered a secondary scene.
High Velocity Blood Pattern:
High velocity blood spatter is typically attributed to gunshot patterns. There are many types of blood patterns and they can be given a qualitative value but not always because of one quantitative indicator such as droplet size. Blood pattern analysis largely relies on human judgement, which is somewhat subjective. It is based on looking at multiple factors within a crime scene and blood pattern analysis is a helpful interpretive tool.
High velocity blood patterns from gunshot wounds have the lowest error rate as compared to medium or low velocity patterns. This is because these patterns have a predominance of blood spatter where the droplets are 1 millimeter in diameter, which is like a misting of blood droplets and easily identifiable. Details like this are critical to crime scene reconstruction.
Patterns are never looked at separately—the analysis must include a whole view of the scene such as position of the body, position of the gun, direction of the spatter and surface where the blood landed. Additionally, any good death investigator always challenges their own hypothesis, even when the evidence appears obvious.
To one extent or the other, every autopsy involves the dissection of the human body. There are various methods of dissection but the most common one in forensic medical/legal investigation is the Virchow method, named for Rudolf Virchow. Born in Germany in 1821, Virchow is known as the founder of modern pathology due to inventing a systematic method of autopsy in which the process starts from the outside in. Each organ is dissected separately and fully examined. For example, once the chest plate is removed then the organs are observed in their position. In general, the heart is the first organ removed and examined, next the lungs are removed, and then the process continues, descending into the lower regions of the body. Once all organs are removed and examined the scalp is reflected backwards, the skull cap is sawed open and the brain is then examined.
During a forensic autopsy, there are numerous collections of samples and certain areas such as structures around the neck are closely examined. A forensic autopsy also involves toxicology and tissue slides. The entire process is documented with photos and a dictated autopsy report from the forensic pathologist.
Forensics means science applied to law. Entomology is the study of bugs. A forensic entomologist is someone who studies insects and a variety of anthropoids. In forensics, this science is connected with the study of decomposition of the human body. Insects are part of the process of decomposition especially the common house fly and their eggs, which become maggots that feed off the decomposing tissue. The study of what is called anthropophagi or the process of bugs eating humans is a complex study that can provide a timeline of where and when a person died. Forensic entomology can play a very important role in crime scene investigation and requires knowledge of the different types and phases of anthropophagic action.
A petechial hemorrhage is a very small dotted hemorrhage caused slight bleeding in the subcutaneous tissues. In medical legal investigation, they often appear in the face and eyelid area in mechanical strangulation cases. They are an artifact of the deprivation of oxygen to tissue. This can be caused by quick suffocation, strangulation and even some natural events. Like all other hallmarks of a particular action, petechial hemorrhage should be corroborated by other markings on the body or findings at the scene.
In every science, there is a language that one must learn. In math that language might be quadratic equations, in medicine and medical legal death investigation there are specific and universal terms used for different types of trauma. It is important for an investigator or a medical professional to use the most accurate words to describe wounds and know the appropriate terminology. Describing a wound properly is critical to the accuracy of a coroner’s report which can be then used as evidence.
A laceration is different that an incise mark, which is what most people call a cut from a sharp object. A cut occurs from the sharpness of the object such as a knife or a shard of glass. A laceration comes from an object coming in contact with the skin with dramatic force.
A laceration has distinctive differences from an incise or a cut. A laceration has roughness around the edges of the wound usually with some bruising. A laceration is a tear caused by force. The laceration will also have bridging of material like collagen or fat cells across the wound. Cuts have smooth edges and no bruising or bridging.
One of my favorite experts is Dr. Vincent DiMaio. His testimony of gunshot wound analysis is a great example of how forensic professionals describe wounds.