Webinar presenter Roxanne Kotzebue answered a number of your questions after her presentation, The Science of DNA – SImplified! What Law Enforcement and Affiliated Professionals Need to Know. Here are some of her responses.
Audience Question: Can DNA be damaged such as through swabbing?
Roxanne Kotzebue: To my knowledge, I don’t believe swabbing would damage DNA for forensic purposes. Most of the time the collection of DNA off an item will involve collecting cells which house the DNA. In the testing process the cells eventually are popped. In addition, during amplification only small segments of the DNA are analyzed, so if the DNA molecule was damaged there is still the capability of developing a profile or a partial profile. However, DNA can be damaged through other means; for example, age, weather, and storage conditions. If an item has been sitting in the sun for years, there is the potential for DNA to be degraded.
Audience Question: In cold cases, how long realistically can DNA stay intact? Does it depend on what the DNA is on?
Roxanne Kotzebue: DNA can begin to degrade due to a variety of conditions. It is going to depend on the type of DNA, the storage conditions, and the type of sample you are looking at. Some years ago scientists were able to examine the DNA of wooly mammoths, which are extinct. For forensic purposes, if you have an extremely old sample, something like bones or teeth may be able to yield a better DNA sample than a shirt that was touched decades ago.
Audience Question: Which are the most effective parts of a firearm for swabbing for DNA?
Roxanne Kotzebue: From talking with different forensic scientists, labs have differing methods on firearm analysis. Some labs like to swab each area individually, such as the trigger, slide, etc. Our lab has success with combining the areas. First, the textured area of the gun is swabbed. Next, the gun is processed for latent prints on the smooth areas. Finally, a second swab is taken of the smooth areas of the gun after printing. This yields good results for our lab and also has the benefit of reducing the number of samples analyzed.
Audience Question: What are your recommendations for prioritizing DNA evidence?
Roxanne Kotzebue: It's going to be up to each individual lab what your priorities are. The most important thing will be communication. A supervisor should be communicating with the various departments and triaging cases. One option would be a priority list. Each department will submit cases and are allowed a certain number of priority cases which would be worked first. As far as triage, each lab should have an idea of the type of cases/amount of samples allowed for DNA analysis. For example, some labs allow only a certain number of samples for burglaries. Some labs do not accept victim items that were moved by a suspect. Discussing what the lab allows with the various departments can allow for a smoother system for DNA requests. In the end, communication is key.
Audience Question: Is there anything else you're aware of that most probably will destroy DNA during producing evidence that in club moss for dusting and extant use of ALS UV light? I want to ask especially about cyanoacrylate fuming does it actually just encapsulate DNA or make an extraction possible?
Roxanne Kotzebue: I am not sure about the club moss. I will have to do some research. Email me and I'll look into this for you. To my knowledge, labs can process an item for DNA analysis after cyanoacrylate fuming.