Methods of DNA Recovery

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I have explained in details the methods of recovery of various samples found in a crime scene, their packaging & transportation protocols & the various tests that are performed once they reach the lab.

DRIED BLOOD STAIN:
It is very common to find dried blood sample in a crime scene. Police investigators make it certain that the sample reaches the lab taking the utmost care with the least possible harm to the sample.
If the blood is found on clothes then the investigator should carefully take a non-absorbent paper and wrap it and then place it in a box, seal it. Investigator at the crime scene should never try to remove the blood from the cloth and try to put in any other solution. After sealing the box it needs to be properly labeled. If blood is somehow collected on a large object then the object needs to be properly wrapped and the edges sealed with a tape to avoid any sorts of contamination that might alter the result. If however, the blood lands on a very large object which is not practical to carry, then investigators should scrape off the sample on a piece of paper and wrap and put the paper in an envelope. A freshly sterile knife should be used to scrape off the sample from the large object.
Blood samples collected on small objects should also be carefully wrapped and the whole object should be transported to the lab. Moist cloth should never be used to collect blood sample.

HAIR:
Hair samples are also very important since it can tell investigators about the race of the individual and also from which part of the body the hair originated. It is important to collect all the hairs present in the crime scene using gloved hands or sterile tweezers. The hair samples should be then kept carefully in envelopes, sealed and labeled properly before transporting to the lab. If the hair is not free but attached to any object like glass, or on any metal, investigators should not attempt to remove the hair but take the whole object to the lab. Just like blood collection procedure, hairs stuck to large objects should be properly wrapped and taped to avoid any sort of contamination from occurring. In rape cases hair from the pubic portion should be combed and collected in an envelope. Around 30-60 pubic hairs are needed for proper examination. If hair need to be collected from the victim or the suspect's head then the person should be asked to bend over a paper and hair over the head should be combed gently and all loose hairs should be collected on a paper and the paper should be properly sealed and put inside an envelope. Hair from the suspect should be collected from all parts of the body.

HANDGUN AND SHELL CASINGS:
Firearm recovered from a crime scene can provide very valuable information to solve the murder mystery. The type of firearm used, the number of bullets fired and the angle from which the shot/shots were fired to kill the victim can give out very precious and useful information to investigators. When dealing with firearm the rule is to never submit a loaded gun to a lab unless it is delivered in person. Cartridges should never be removed from the magazine and the magazine should be always removed from the gun before transferring the gun to lab. Even if a gun is on safety mode still guns should not ...