How should DNA be collected from a crime scene?

Many movies would have surely encouraged us to take up detective work....isn't it? Well, we need to be very clever in collecting the evidence. We shouldn't do many things which detectives or officers do in movies while collecting proofs....So "How should DNA be collected from a crime scene?"

It is a fact that even a criminal wearing gloves may unwittingly leave behind trace amounts of biological material. It could be a hair, saliva, blood, skin, sweat, mucus or ear wax.

As with fingerprints, the effective use of DNA may require the collection and analysis of elimination samples. It often is necessary to use elimination samples to determine whether the evidence comes from the suspect or from someone else. An officer must think ahead to the time of trial and possible defenses while still at the crime scene. For example, in the case of a residential burglary where the suspect may have drunk a glass of water at the crime scene, an officer should identify appropriate people, such as household members, for future elimination sample testing. These samples may be needed for comparison with the saliva found on the glass to determine whether the saliva is valuable evidence. In homicide cases, be sure to collect the victim's DNA from the medical examiner at the autopsy, even if the body is badly decomposed. This may serve to identify an unknown victim or distinguish between the victim's DNA and other DNA found at the crime scene

 All it takes is a few samples to obtain enough DNA information to identify a suspect. Police officers and detectives often work closely with laboratory personnel, or evidence collection in technicians, to make sure evidence is not contaminated.

This involves wearing gloves and using disposable instruments, which can be discarded after collecting each sample. While collecting evidence, officers are careful to avoid touching areas where DNA evidence could exist. They also avoid talking, sneezing, and coughing over evidence, or touching their face, nose, or mouth. When a crime has been committed outdoors, the entire area is covered by a tent to stop material from being blown on to the area by wind, or being washed away by rain. 

When investigators find a piece of evidence they place it in a paper bag or envelope, not in a plastic bag. They label the bags with information about what the material is, where it was found, and where it will be transported. It is then analised in a forensic laboratory.

When transporting and storing evidence that may contain DNA, it is important to keep the evidence dry and at room temperature. Once the evidence has been secured in paper bags or envelopes, it is be sealed, labeled, and transported in a way that ensures proper identification of where it was found and proper chain of custody. They never place evidence that may contain DNA in plastic bags because plastic bags will retain damaging moisture. Direct sunlight and warmer conditions also may be harmful to DNA, so avoid keeping evidence in places that may get hot, such as a room or police car without air conditioning.

This is definitely very tough! I truly salute their job...Doesn't these all sound tough?

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