In recent times, science has provided substantial aid to crime detection. Because anything in the physical universe has the potential of becoming an item of evidence in an investigation, a wide variety of procedures may be used in analyzing and interpreting evidence in a criminal case. These procedures include handwriting analysis, forensic photography, crime scene documentation, metallurgical investigations, chain of custody, entomology, and blood spatters.
The first thing you do after securing a crime scene is document it. Always take pictures. They are the best records available. They show the crime scene as it was found; where objects are in relation to other objects, victims, rooms, etc.
Take notes. Describe the scene, it’s over all conditions. Describe rooms, lights, shades, locks, food; anything that can indicate a time frame, condition of scene or that might have even the slightest evidentiary significance. Check dates on mail and newspapers.
Diagram the crime scene. Take measurements. Photos are good to show where an object is in relation to another object, but measurements tell exactly how far. True handwriting analysis involves painstaking examination of the design, shape and structure of handwriting to determine authorship of a given handwriting sample.
The basic principle underlying handwriting analysis is that no two people write the exact same thing the exact same way. Every person develops unique peculiarities and characteristics in their handwriting. Handwriting analysis looks at letter formations, connecting strokes between the letters, upstrokes, retraces, down strokes, spacing, baseline, curves, size, distortions, hesitations and a number of other characteristics of handwriting. By examining these details and variations in a questioned sample and comparing them to a sample of known authorship, a determination can be made as the whether or not the authorship is genuine.
Another is, Metallurgical Investigations–examinations make it possible to identify the source of an item—whether made of metal, plastic, ceramic, or other material—found at a crime scene, and further, to determine if two similar items were fractured from each other, the nature of the force causing the fracture, the direction from which the force came, and the time when the fragments became separated. Such identification helps trace the evidence to its owner. The metallurgist can also restore obliterated or altered numbers on objects of any material. Mineralogical Investigations is the science of mineralogy is also used in crime detection.
The mineralogist studies soil, plaster, cement, brick, concrete, and glass for any evidence. Mineral analyses have shown that differences may be detected in soil composition. Soil and dust found on a suspect’s clothing and determined to be comparable to that at the crime scene help to prove the person’s presence in that locality. Toxicology may be defined as the science of poisons special methods of analytical chemistry have been developed for use in toxicological examinations.
The specimens ordinarily examined in cases of suspected poisoning are tissue samples from vital organs, blood or urine, food, drink, and the suspected poison itself. Firearms are identified through microscopic imperfections that are produced inadvertently in gun barrels during manufacture. Subsequent use and wear contribute further to a weapon’s individuality. Chain of Custody is of paramount importance to any investigation.
It is the unbroken sequence of events that is caused by an item of evidence from the time it is found at the crime scene to the time it appears in court. Every link in this chain is documented, from discovery at the crime scene, through evidence gathering, storage, and lab analysis return to storage, and transfer to court. Every link is documented by date, time, and handling individual, what was done with the evidence by that individual. If chain of custody is broken, if the evidence cannot be accounted in one step of its journey from crime scene to courtroom, it is rendered inadmissible; useless to the case.
Blood spatters help a great deal in reconstructing a crime scene. They can be used to corroborate or disprove and alibi. They can be used to convict the guilty. There is much more to it than looking at a stain or spatter and saying, “This is where the crime took place.
” The patterns of the spatters and the shapes of the individual blood droplets themselves can tell how the crime was committed. Drops falling from different heights (i.e. at different speeds) will leave different looking spatters.
A drop falling from a low height of a few inches will leave a small cohesive circle. At greater heights, the circle will be larger and may even have a ‘crown’ effect. Hitting a surface at an angle does even more to disrupt a blood droplet. Perpendicular impact leaves a droplet fairly uniform, as shown below.
A droplet hitting a surface at an angle will bulge out in one direction, indicating the direction of travel of the droplet. Cast off stains is a result of blunt force trauma (beating with an object such as a hammer). Pulling back from a blow produces a blood spatter that indicates direction, by creating an arc of blood droplets. You can determine the number of blows inflicted by counting the arcs.
You can also determine the orientation of the individuals involved the size of the object used and the right or left handedness of the assailant.