Forensic Swabs For Crime Scene DNA Evidence

Advancing Swab Science

Throat swab used to diagnose diphtheria, England, 1901-1930
Puritan Sterile DNA Controlled Cotton Swab with Transport Tube P25-806-1PC-BT-FABUSA
Puritan Sterile DNA Controlled Cotton Swab with Transport Tube P25-806-1PC-BT-FABUSA used as a forensic swab and diagnostics.

For many years, fingerprints evidence was the standard for investigating and linking suspects to a crime scene. Rapid evaluation of forensic swabs science has shaped DNA evidence as the gold standard.

A few cells are all an investigation team needs to obtain in order to get enough DNA information to identify a suspect.

DNA analysis has been helping law enforcement agencies solve crimes for more than three decades.

DNA swabbing plays a critical role in streamlining crime scene investigation. They enable forensic professionals to extract valuable information from even the smallest samples of saliva, urine, blood, and other tissues.

However, it is important to consider that the effectiveness of forensic analysis depends on the quality of sample collection tools and methods. Low-quality sample collection, storage and transportation media can lead to potentially invalidated results.

How to swab for DNA evidence

The collection of DNA evidence is a highly effective technique used worldwide to solve investigations.

It is essential for medical examiners, forensic scientists, and crime scene investigators to master DNA specimen collection methods.

At a crime scene, both physical evidence, such as a weapon, and biological evidence such as sweat or blood could yield DNA samples. If someone touched a weapon or object, various forms of touch DNA might have been left behind.

In case the crime scene provides a clear source of DNA, the sample can be collected using proven tools like swabs. Here is a simple process to swab for DNA evidence:

Preparation

Preparation is the first step you should take to ensure effective DNA swabbing. Make sure your staff is well-trained and well-equipped. Approved personal protective equipment (PPE) such as gloves (and possibly even shoe covers, hair nets, and masks depending on the scene) must be used during DNA swab collection.

Proper preparation will help you avoid contamination of samples which can become a critical issue in court proceedings.

Sterile swabs, distilled water, transport media, evidence tape and flashlights are some of the essentials your evidence collection kits should contain.

Swabbing

Swabbing is a preferred DNA sample collection method over taping. There are swabbing techniques used in accordance with the sample type (touch DNA, blood, sweat).

No matter the swabbing methods you implement, change gloves and forceps after each item is necessary to prevent cross contamination. Following are the three most popular techniques:

  • Swabbing for touch DNA
  • Double Swabbing for touch DNA
  • Swabbing bodily fluids like blood

Preserving Forensic Swabs

One of the most important parts of collecting cells is ensuring that the swab is completely dry during preservation and transportation. Some of the modern collection tubes are designed to ensure both effectiveness and convenience in preserving samples.

Here are some tips that will help you conduct a reliable DNA evidence collection process:

  • Wear protective gloves before removing the swab from its wrapper
  • Touch only the handle of a forensic swab
  • Pre-moisten the swab with sterile distilled water if the sample is dry
  • Place the tip of the swab on the surface and rotate it gently to allow tissues to absorb into the fibers
  • Put the swab tip-first into appropriate packaging and allow the sample to dry

There are several environmental factors such as temperature, mold, and bacteria that can affect the DNA at the crime scene.

Follow the pre-defined DNA collection procedures even if the crime scene has been compromised.

Use DNA-Controlled Swabs

When the job is to swab for evidence at crime scenes, you can choose from a number of techniques. But when it comes to DNA evidence collection, it is recommended to use DNA-controlled or DNA-free buccal swabs.

If the swab is not free of human contaminants like DNase and DNA, it could compromise the sample, and consequently, the case.

Therefore, always use buccal or DNA swabs certified by an independent laboratory.

Following are two popular types of buccal swabs used widely at crime scenes:

Flocked Swabs

HydraFlock® Flocked Sterile Swab, Elongated Tip P25-3806-H-2
HydraFlock® Flocked Sterile Forensic Swab, Elongated Tip P25-3806-H-2

DNA-free flocked swabs are ideal when you have to deal with an extremely small sample size.

Flocked swabs are being increasingly used for forensic processes due to their unique structure which helps crime investigators collect, retain, and elute specimen better than other low-quality swabs.

A flocked swab is also handy when it comes to collecting touch DNA from fingerprints or skin cells, or residue from arso, gunshots, or explosions.

Cotton Swabs

Puritan Cap-Shure Sterile Cotton Forensic Swab: 25-806-1WC-EC

If the sample is large enough and there is no need for advanced collection and elution, a sterile cotton swab, either with polystyrene or wooden handle, will do the job.

If it is not required to transfer the sample to FTA cards, it is recommended to use cotton swabs, not only for DNA collection but also for other medical applications.

About Harmony Lab & Safety Supplies

Need a forensic swab supplier? Harmony can help. Get premium quality buccal swabs ideal for collecting DNA samples from crime scenes.

Forensic professionals have been relying on Harmony for our large collection of cost-effective swabbing solutions.

Available with cotton, flocked and foam tips, our forensic swabs are certified for forensic work and tested to the most stringent standards.

Visit our online store to learn more about our collection of forensic swabs.

Sterile Swabs for DNA Collection

Sterile Swabs for DNA Collection

The Importance of Choosing the Right Sterile Swabs for DNA Collection

DNA is a molecule found in humans and virtually every other living thing on the planet. Through this hereditary material, testing companies can discover a world of information about any given individual. Virtually all cells in the body carry the same DNA, but the cheek is often used as the primary site for collecting DNA.

Swabbing the cheek is an approach widely used across a number of applications, including paternity testing, criminal investigations, and determining ancestry. This method is preferred because it’s non-invasive, unlike blood tests. (As you might imagine, it’s a welcome alternative for needle-averse individuals!) The cheek is also an ideal site for testable genetic material, as a wealth of DNA can be retrieved from just a small sample of saliva.

That said, there are some considerations to be mindful of when it comes to using cheek swabbing to extract DNA. Most importantly, you need to have the right tools.

You might think that all swabs are created equal, but that’s not the case when it comes to DNA testing. It turns out these little swabs play a major role in achieving accurate DNA results. In fact, a study published by the Journal of Forensic Research confirmed that the tightness of cotton found on sterile swabs can actually impact the odds of creating conclusive DNA profiles.

Thus, if your situation is critically important – for instance, you’re ruling out a suspect in a homicide case – there’s absolutely no room for mistakes!

So, choosing the right sterile swabs is a critical component in ensuring accurate DNA results. But can’t you just use the regular cotton swabs found at the grocery store to retrieve DNA?

In theory, you could but the results would be less than perfect.  The swab is likely to return inconclusive results.  At a minimum when you’re collecting a DNA sample the swab should be sterile.

This eliminates contaminants that may cloud your results.  Optimally, you should use a DNA Free swab that is tested and certified to be DNA free.

When it comes to selecting the right sterile swab, you have some choices. While they all serve the same purpose, swabs can be made from different materials. We’ll explore each below, along with its properties and pros and cons.

Foam Sterile Swabs

Puritan Sterile Foam Tip Swab 25-1805-RND-2
Puritan Sterile Foam Tip Swab 25-1805-RND

Foam-tip sterile swabs, as their names suggest, have foam ends designed to capture the cells found inside a person’s cheek (also known as buccal cells). The foam is highly absorbent, which is ideal for collecting and retaining saliva. Since they’re non-abrasive, they won’t cause any discomfort to the DNA donor.

Their gentle tip also makes it easy for nurses and medical professionals to rub the swab thoroughly in the cheek pocket and near the gum line, where saliva often accumulates.

Among all the types of sterile swabs, foam tip swabs have the highest particle collection capacity. Their porous nature allows them to capture a high-quality DNA sample, and the retrieval process is equally efficient. When lab workers need to release the sample, all they’ll have to do is elute the foam tip into their preferred buffer method.

Foam tip swabs are also available in a variety of different sizes to accommodate all types of donors and applications. Small and regular tip sizes available, and the tip also comes in different shapes, including standard, rectangular, and round.

You can also choose among different shaft materials, including plastic and polypropylene. To preserve sterility, each swab is individually wrapped.

Flocked Sterile Swabs

HydraFlock® Flocked Sterile Swab, Elongated Tip P25-3806-H-2
HydraFlock® Flocked Sterile Swab, Elongated Tip P25-3806-H

Like foam tip swabs, flocked sterile swabs have superior collection and release characteristics. Although they aren’t as absorbent as the foam tip swabs, they feature unique flocked fibers which make collection and elution simple and effective.

Polyester flock swabs are commonly used in buccal cell collection, and due to their excellent absorption and elution capabilities, they are the go-to options for rapid diagnostic testing.

Flocking refers to a process of applying short fibers to an adhesive-coated surface, resulting in a swab with a velvet-like brush tip.

Their flocked fiber tip structure also makes them a gentler alternative to foam and cotton sterile swabs. Thus, they can be used even in newborns, and their collection characteristics make it possible to collect saliva even in children whose salivary glands may not be developed.

These, too, come in a variety of options. Tip sizes range from mini (18.4 by 3.4 mm) to large (16.2 by 5.3 mm) to even elongated (17.3 by 5.5 mm). Flocked sterile swabs are also pre-packaged to prevent contamination.

Cotton Sterile Swabs

Puritan Sterile Large Tip Cotton Swabs P25-806-10WCL
Puritan Sterile Large Tip Cotton Swabs P25-806-10WCL

Finally, there’s the swab everyone knows and loves: the cotton swab. Again, these medical-grade cotton sterile swabs are far different from those you use at home.

Not only do they feature longer shafts for convenient cell collection, they also may be produced in cleanroom environments to prevent any possibility of DNA contamination.

By nature, cotton is a bit more abrasive than the foam and flocked swabs described above. Yet, that can be an advantage for DNA collection – it provides ample friction for releasing buccal cells. It’s also still gentle enough to prevent any discomfort.

Cotton sterile swabs are also versatile because you can either elute the swab in a buffer or remove the tip and drop it into a vial. Like the varieties described above, cotton sterile swabs are available in a variety of sizes and quantities, and are packaged individually.

Choosing the Right Sterile Swab

Now that you’re familiar with the different swab options available for DNA collection, which will you choose? Here are some factors to consider before making your decision:

  • Do you need an ample DNA size for your application, or will it suffice to have a small sample?
  • How old are the donors from whom you’re collecting DNA?
  • Will a professional be collecting the DNA, or will the donor themselves be performing the retrieval?
  • Is the sterile swab going to be part of a kit?
  • Will the samples be transported, or will the tests be performed on premises?

No matter your unique needs, Harmony Lab & Safety Supplies has the right sterile swabs available for your DNA/buccal cell retrieval purposes. With dozens of materials, sizes, shapes, and quantities to choose from, we have a diverse selection of low-cost swabs available.

All of the options listed above are available at HarmonyCR.com, where you can view each swab’s specific properties to make the best selection for your business.

If you’re still unsure on which swab is perfect for you, give our supply specialist a call and they’ll be glad to help you choose the right swab for your needs.