Forensic Science
Sherlock Holmes, from the Arthur Conan Doyle stories
Sherlock Holmes, a fictional
detective of a century ago, was one
of the first to use forensic science
the scienific analysis of physical evidene to solve crimes. Holding a
big magnifying glass, Holmes inspected crime scenes for footprints, broken glass, hair-
anything that might help identify the person who committed the crime. In today's world,
Holmes might be a CSI, or crime scene investigator.
Today, when a crime is reported, a murder for instance, the police immediately
send a Medical Examiner (ME) and a CSI team to the crime site. The ME and CSIs will be part
of a panel of technical experts in the investigation.
At the crime scene, the ME examines the body of the victim and looks for wounds
or marks that might be related to the crime. The ME also takes many photographs of the
body. The body is subsequently taken away for a detailed examination that will establish
the cause and time of the victim's death.
Meanwhile, CSIs first take hundreds of photographs of the crime site. Next they
check the site for fingerprints. Most fingerprints form when sweat or another oily substance
on a fingertip leaves an invisible imprint on a glass, tabletop, or other object. CSIs dust a
black powder on objects at the crime site to make these prints visible. The CSIs then look
for drops of blood, strands of hair
pieces of ripped cloth, or other evidence that might link
someone to the crime site.
"Every contact leaves a trace," according to an authority in forensics. This means
that whenever a crime involves physical contact, the criminal either leaves something at the
site, takes something from the site, or both. This might be any number of substances,
including hair, animal fur, sand, grass, and fibers from clothing or carpeting. Such trace
evidence is usually difficult to detect, so, like Sherlock Holmes, CSIs rely on handheld
magnifying glasses to examine the crime sc
CSIs might even vacuum the entire area to
collect tiny samples. They carefully label each piece of evidence as they collect it.
The collected evidence is then sent to a forensics laboratory. There, forensic
scientists will analyze it to establish how and when the murder took place, where it took
place, and who did it. Sometimes the evidence will even show why it took place, that is,
the motive for the killing.
Among all the evidence found at the site, fingerprints are conclusive in linking a
specific person to the crime scene. This is because no two people have the same
fingerprints. Fingerprints from a crime scene are analyzed by computer to determine if they
match the prints of known criminal or crime suspect. Fingerprints are vital evidence.
DNA is another conclusive means of identification because each person's DNA is
unique.
DNA is contained in cells of the body, s
that evidence of har, blood, tears,sweat
or other bodily fluids found at a crime scene can be used to link a specific person to the
crime. Like fingerprints, DNA samples are analyzed by computer to determine if they match
the DNA of a known criminal or a suspect.
Voices, too, are unique. Samples of voices from security camera tapes, telephone
answering machines, or other recording devices can be scanned electronically. A printout of
the scan will show patterns of highs and lows, rhythm, and volume that can be compared
to patterns of a suspect's
voice. However, authorities have contrary opinions about using
voiceprint
for identification. Some argue that voices can change over time as people age or
suffer illnesses, so old voiceprints are not always reliable.
In the laboratory, forensic scientists use an electron microscope to scan samples of
the substances that were collected at the crime scene. Then they enlarge the samples (up
to 150,000x) on a visual display unit. This allows them to easily compare those samples with
samples found at another location or on a suspect's clothing.
Forensic laboratories have on file the shoe print patterns of thousands of kinds of
shoes. These can be compared to shoeprints found at a crime scene to establish the size
and kind of shoes worn by a suspect. If the shoeprint was made in a soft material, like mud,
the lab may be able to tell the height and weight of the person by the depth of each step
and the distance between steps.
After all of the evidence has been analyzed, the police chief consults with p
ane
members. Based on the evidence, they determine if it is logical to accuse and arrest a crime
suspect. If it is, members of the panel may later be asked to present their forensic evidence
in a court of law as proof of a suspect's guilt.