Crime Detection


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.