Crime Scene Investagation

DNA

DNA is a self-replicating material presents in nearly all living organisms as the main constituent of chromosomes.

Chromosomes

Chromosomes are a thread like structure of nucleic acids and proteins found in the nucleus of most living cells, carrying genetics information in the form of genes.

Gene

A gene is the basic physical and functional unit of heredity, Genes, which are made up of DNA act as instructions to make molecules called proteins.

How are all these testing procedures helpful in a crime scene?

They are all helpful for finding identification, and its essential that first they would be located, processed and, recovered.

Drawing Blood Fingerstick procedure
  • When the site is selected, put on gloves and clean the selected puncture area
  • Using a sterile safety lancet , make a skin puncture just off the center of the finger pad. The puncture should be made perpendicular to the ridges of the fingerprint so that the drop of blood does not run down the ridges.
  • Wipe away the first drop of blood, which tends to contain excess tissue fluid
  • Collect drops of blood into the collection tube/device by gentle pressure on the finger. Avoid excessive pressure that may squeeze tissue fluid into the drop of blood.
  • Cap, rotate and invert the collection device to mix the blood collected. Then have the patient hold a small gauze pad over the puncture site for a few minutes to stop the bleeding.
Fingerprint Process
  • First clean off the person's finger with an alcohol wipe to remove any sweat. Then make sure it is dried throughly
  • Then have the person rolls his or hers fingertips in the ink to cover the entire fingerprint area.
  • After each finger is rolled onto prepared cards from one side of the finger nail to the other. (these are called rolled fingerprints)
  • Finally, all fingers of each hand are placed down on the bottom of the card at a 45-degree angle to produce a set of plain (or flat) impressions. (these are used to verify the accuracy of the rolled impressions.)
DNA Swabbing
  • For buccal swabs, scrape your inner cheek with a sterile swab for up to one minute. Once finished, be sure not to touch the end of the swab to any surface other than the inside of the container.
  • Collect other samples using the same precautions. If you plan on collecting less common samples, such as fingernails or blood take every precaution to avoid touching or otherwise contaminating them. Check with the lab you plan on sending the specimen to in order to confirm that they are able to extract DNA from the sample you are collecting.

References:

  • http://www.crimemuseum.org/crime-library/blood-evidence-collection-and-preservation/
  • https://ghr.nlm.nih.gov/primer/basics/gene
  • https://ghr.nlm.nih.gov/primer/basics/dna
  • https://ghr.nlm.nih.gov/primer/basics/chromosome
  • http://science.howstuffworks.com/fingerprinting2.htm
  • https://www.geisingermedicallabs.com/catalog/blood_specimens.shtml
  • http://www.wikihow.com/Collect-DNA

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