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CSI Facts
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What is CSI?

Crime scene investigation is a science known as forensics. For every crime there is a series of evidence left behind that can lead authorities to the facts behind the incident. Skilled professionals analyze every bit of the area until they know all the details of a crime including, sometimes, who did it. Let's take a look at this fascinating job and the science behind it.


dectective tools


The word forensic comes from the Latin word forensic meaning public or to share with the public as in sharing the crime with the court system. Any science that is used for the intention of law related issues is a form of forensic science.

The Process

A forensic scientist studies lots of evidence at the scene. Their first line of fact finding is to talk to anyone who was a witness or might have been a witness without realizing it. This can give them important clues. Sometimes the victim makes a good witness. PhotographBut because people can forget or remember events incorrectly, physical evidence is usually more reliable.

Try this with a friend. Show your friend a photograph containing a number of people - say 3 or 4 - doing something in a location not familiar to your friend. Allow them to look at the picture for under a minute. Don't tell them why. Then ask them detailed questions about the picture. What color was the hair of the tallest person in the picture? What was the person wearing that was sitting? Which person had a hat? See if your friend caught all the details you are searching for. See why witnesses don't always get everything right. They didn't realize they were going to be a witness when the event was happening. Fear and other emotions can also affect a person's memory.


Some of the evidence that can exist at a crime scene:

  • soil
  • glass
  • plants
  • fibers
  • fingerprints
  • tire tracks
  • splatter
  • footprints
  • liquids
  • chemicals
  • handwriting
  • drugs
  • bullets
  • hair
  • blood
  • DNA
  • broken or bent objects

These are just a few of the things that a forensic scientist might find and study at a crime scene.


Cross Contamination

When studying a crime scene, it is extremely important that evidence doesn't get cross contaminated. This means that evidence doesn't get mixed with other evidence or touched by people who are on the scene. For this reason crime scene tape is placed on the sight to keep people from walking or touching the area being investigated. Investigators take other precautions too, like wearing gloves so their own fingerprints don't end up on the evidence. Each piece of evidence that they collect is stored in a separate plastic container before taking it into the crime lab to study further.

Evidence gathering


crime scene tape

Other Challenges

Outdoor crime scenes present some difficult challenges for investigators. Animals or other humans can accidently cross through a crime scene and destroy evidence before the investigators get word that a crime has been committed, especially in public outdoor areas like parks. Time is crucial and having to investigate an outdoor crime scene at night when it is dark may cause forensic experts to overlook important evidence. But waiting until morning light means that weather conditions like rain or temperature changes can alter evidence.

When is it used?

TV programs would have most people thinking that crime scene investigators are hunting for clues in a murder or a kidnapping. That is often done, but forensic scientists can solve cases of burglary, break-in, car jacking, poaching, bank robberies, fraud, forgery, traffic accidents, and many other crimes. Forensic scientists have even been called on to identify dinosaur bones, crimes committed centuries ago or to determine the cause of death for historical celebrities such as ancient kings and pharaohs.




DNA and Fingerprints

DNA is often used to identify victims or suspects or to rule out people involved in criminal activities. But what is DNA and how can it be used in such instances?

DNADNA is like a secret code that exists in all of our cells. DNA is a microscopic plan that structures details about us such as what we look like, what hand we write with and even how tall we will grow to be. Everyone and every living thing have DNA. No two people have the same DNA unless they are identical twins. Because every DNA is different, it may someday be used for investigators to identify all details of a person from their hair color to their talents. Scientists are currently working on identifying all of the secrets that DNA holds. To learn more about how DNA is used in forensic work, check out this web site.

fingerprintIn forensics, scientists can take a sampling from the inside of someone's cheek or their blood and compare the DNA of one sample to the DNA of another sample to be able to tell if they came from the same person. This can be very helpful in proving that a suspect is actually NOT guilty. This method of crime solving has been used regularly since 1992.

Fingerprints are the small ridges on the tips of our fingers and are different on every person. When a person touches a table or another surface, they leave behind a telltale sign of their fingerprint. Forensic investigators can then remove this fingerprint using a special powder and some tape. They then compare this evidence with a fingerprint that has been collected from the person to whom they are planning to compare. Fingerprint specialists evaluate the small curves and whorls of the fingerprints to determine if they are the same. There are a series of fingerprint patterns which are similar in all people. Take a look at these patterns to learn more about fingerprinting.

Wildlife Forensics

Fox and henCrime in the animal world happens more than most of us know. Forensic investigators use the same methods and tools as those who solve crimes against people. They can find out how the animal died, how long ago it happened, and track down if it was killed by another animal or by a human. By teeth marks and hair left at the scene they can even figure out what kind of animal did the killing. Sometimes it is important to find out if a wolf or a bear is killing farm animals or in an area frequently visited by hikers or campers. This is a safety issue for all of us who love the outdoors.

Slain birdAnimals are sometimes hunted illegally. This is known as poaching . A forensic scientist can use evidence left at the scene to help authorities arrest the person or the people who killed an endangered animal, hunted more than they were permitted, or who was hunting outside of the rules.

To learn more about wildlife forensics visit Idaho Fish and Game's forensic website.

Want To Be a Forensic Scientist?

Here are just a few of the possible jobs available in the world of forensic science:

  • medical examiner - performs autopsies
  • chemist - analyzes chemicals found
  • forensic engineer - might determine how a structure collapsed
  • toxicologist - tests for poisons
  • DNA analyst - uses DNA to identify victims or suspects
  • lab technician - studies blood and other body samples
  • computer technician - records information for safe keeping
  • fingerprint expert - can identify specific patterns in fingerprints
  • handwriting expert - can determine handwriting patterns
  • psychiatrists - study crimes for determining prevention in the future
  • anthropologists - study bones to determine age, gender, race, etc.
  • ballistics - determine the gun and ammunition used in a crime

Magnifying glassLots of other professionals can be called on in particular situations including plumbers, electricians, nurses, doctors, dentists, and anyone else who might have information specific to the details of a case.

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