What is a Forensic Swab?
A forensic swab is a simple cotton swab used by forensic scientists and investigators to collect DNA evidence from crime scenes. Swabs are commonly used to collect epithelial cells from areas like the mouth, cheeks, or under fingernails which may contain DNA from a suspect.
Collecting DNA Evidence
It play an important role in collecting DNA evidence left behind at crime scenes. When a person touches an object or surface, they leave behind epithelial cells containing their DNA profile. Investigators use sterile cotton swabs to carefully rub or swipe the targeted area to collect any deposited cells. The swabs are then sealed and sent to a crime lab for analysis. At the lab, technicians extract the DNA from any cells on the swab and analyze specific locations on the DNA known as Short Tandem Repeats, or STRs, to develop a DNA profile. This profile can then be checked against DNA databases to potentially identify the source.
Types
There are a few different types of swabs commonly used for DNA collection:
- Buccal (cheek) swabs - Used to collect reference DNA samples directly from the inner cheeks by gently rubbing the swab along the inner mouth area.
- Fingernail swabs - To collect any epithelial cells or foreign DNA that may be trapped under a suspect's fingernails from scratching or grabbing a victim.
- Fabric swabs - For absorbing DNA evidence left on fabrics, clothes, or other porous surfaces that may have come in contact with a person's external body surfaces.
- Cutting swabs - When significant amounts of biological evidence like blood or semen stains are present, cutting swabs are used which have a small plastic guard or tube to protect the swab and collect a precise sample from the cutting.
Proper Collection and Processing
Proper collection and processing of Forensic Swab samples is crucial to obtaining high-quality DNA evidence. Swabs should be air dried completely before sealing to prevent the growth of molds or bacteria that could degrade DNA. Contamination is also a major concern, so investigators wear protective gear and change gloves regularly. At labs, stringent protocols are followed to analyze swabs separately and keep paper trails to avoid any mix-ups. Even the smallest trace amounts of foreign DNA left behind can provide important leads if collected and analyzed correctly using forensic swabs.
Applications in Solving Crimes
Unsurprisingly, they have played a vital role in solving some high-profile crimes over the years:
- In the Golden State Killer case, investigators were finally able to identify the culprit Joseph DeAngelo after using DNA collected from decades-old crime scenes left on fabric cuttings and comparing it to samples on a public genealogy database.
- O.J. Simpson murder trial - Prosecutors relied heavily on DNA evidence collected from blood drops at the crime scene, Nicole Brown Simpson's condo, and a bloody glove and sock found outside O.J.'s house to argue his guilt had he been convicted.
- 9/11 Terror Attacks - Swabs were taken from the World Trade Center debris and used to identify over 1,000 victims and allowed closure for many grieving families who could not visually identify remains.
- Hadden Clark Murder - Fabric swabs collected from the crime scene vehicle's front passenger seat helped convict Benjamin Smoot for the strangulation and murder of Clark despite Smoot's denial of ever being in the vehicle.
As DNA databases expand and new techniques emerge, forensic swabs will only grow more valuable for solving unresolved crimes well after the fact by generating new leads through familial searches or new DNA profiles being added. Their usefulness at the front end of investigations should not be overlooked either to develop targets or rule out suspects.
the low-tech cotton swab has become nothing short of indispensable in modern criminal investigations. Through diligent collection and stringent processing, trace DNA can be lifted from just about any surface touched by human hands and shed epithelial cells. With new connections to genealogy websites, forensic swabs provide a continuing avenue to solve decades-old cold cases. They exemplify how forensic science has dramatically shifted criminal justice by augmenting traditional evidence categories with compelling biological profiles
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Alice Mutum is a seasoned senior content editor at Coherent Market Insights, leveraging extensive expertise gained from her previous role as a content writer. With seven years in content development, Alice masterfully employs SEO best practices and cutting-edge digital marketing strategies to craft high-ranking, impactful content. As an editor, she meticulously ensures flawless grammar and punctuation, precise data accuracy, and perfect alignment with audience needs in every research report. Alice's dedication to excellence and her strategic approach to content make her an invaluable asset in the world of market insights.
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