Outside the Lab

When one thinks of Forensic Science, the lab comes to mind. What if I told you that Forensic Science could be applied outside of the lab? It is all part of the criminal investigation process and the reconstruction of the crime scene. The evidence found at the crime scene tells a story that allows Forensic Investigators to reconstruct how the crime occurred.

Reconstruction is the formulation of a best theory of a set of events, based on the consideration of all the available evidence and information. In order to reconstruct the crime scene the sequence of events must be understood. Patterns help to establish one’s understanding: blood patterns, glass fracture patterns, track and trail patterns, gunshot residue patterns, trajectory patterns, fire burn patterns, and modus operandi.

Blood makes a predictable pattern due to its make-up, viscosity, density and other physical properties when it exits the body: low, medium, and high velocity. Low velocity is created only by the pull of gravity; if the person is stationary than the blood will pool; if the person is moving, the blood droplets could tell investigators the direction the person was moving. Medium velocity blood droplets are smaller than low velocity and more numerous: approximately 4 mm in diameter. These droplets occur when an object hits pooled blood. High velocity droplets are even smaller than medium velocity and more numerous: approximately 1 mm in diameter to fine mist. This pattern is typical of gunshot wounds and explosions. Blood spatter pattern is the most common type of reconstruction pattern.

Gunshot residue patterns allow investigators to determine the distance of the shooter. When a firearm is discharged, the force of expanding gases disperses materials from the firearm. Depending on the distance, different characteristics will appear. If the wound is a contact wound, one will see blast destruction such as tearing of the clothes or skin and soot and powder inside the garment or the wound. As the shooter moves further away, then the appearance of soot (smudging) around the wound becomes less dense; tattooing on the skin, which are powder particles embedded in and under the skin, begin to loosely adhere to the surface the further the distance.

Because of these predictable patterns, Forensic Investigators can predict the sequence of events while at the scene. Such patterns could also lead to the body if one was not found at the primary scene. To be thorough, the Investigators will perform experiments in the lab to give corroborative evidence: physical evidence that differs from but strengthens or confirms other evidence.