Posts

Detective I. Will Gitterdone had a spotless attendance record, never missing a day for sickness in his entire thirty-three years with the department. In fact, in all of his years of wearing a badge and toting a sidearm he refused to soil that record even though on this particular day his fever hovered at 102, and coughing and sneezing fits forced him to spend the majority of the morning with his mouth and nose buried deep into a crumpled and quite yucky handkerchief. His arms and legs felt heavy and his muscles felt as if he’d been trampled by a hundred stampeding wild pigs.

In spite of the aches, fever, chills, and perspiring like a Savannah ditch digger working in August midday sunshine, Gitterdone was busy collecting suspected blood samples (brownish-red stains for the official record) at a particularly brutal homicide scene. He was also spewing misty spittle via alternating coughs and sneezes. His partner, Al Lergictowork, told him he looked worse than bad and asked if he needed a break. Gitterdone promptly turned his head away from Lergictowork to fired off a round of lung-clearing ah-choo’s directly into the large paper bag of already-collected evidence. “No,” he said. “I’ll be okay. Besides, I’m almost done here.”

So, did you notice anything particularly wrong with Gitterdone’s method of evidence collection? Was there anything he should have done differently?

Well, I think it’s safe to say that it might be a good idea to have both Gitterdone and Lergictowork study this list of Crime Scene Do Nots. It would also be wise to have your protagonist take a peek, just in case.

Crime Scene DO NOT’S

1. Do Not blow away excess fingerprint powder! Doing so adds your DNA to the surface.

2. Do Not use Styrofoam to package electronic devices (computer parts, etc.) because it can cause static charges. Instead, use foam padding or bubble-wrap.

3. Do Not alter or add anything to a crime scene sketch after leaving the scene. Memories are not quite as accurate as we may think.

4. Do NOT place bloodstained evidence in plastic bags. Plastic bags and containers can serve as incubators for bacteria, which can destroy, alter, or deteriorate DNA. Rule of thumb—paper bags/containers for wet evidence (blood, semen, saliva, etc.) and plastic for dry evidence.

5. DO NOT collect DNA evidence samples (saliva, blood, etc.) from a criminal suspect without a court order, the suspect’s consent, or under exigent (emergency) circumstances.

Hapci-fr
6. Do NOT cough, sneeze, exhale, etc. over any evidence sample. This includes talking over a sample. With each word spoken comes your DNA that’s instantly transferred to the evidence.

7. Do NOT fold wet documents. Leave that to the professionals in the lab.

8. Do NOT use fingerprint tape or lifters to collect bits of trace evidence. The adhesion on print-lifting tape is typically insufficient for picking up tiny bits of evidence.

9. Do NOT use dirty digging tools when collecting soil samples. Always clean tools thoroughly after each use to avoid cross contamination.

10. Do NOT use fingerprint lifters in lieu of gunshot residue (GSR) collection materials. (see number 8 above)

11. Do NOT allow shooting suspects, victims, witnesses, etc. to wash their hands or rub them against other surfaces until after GSR tests/collection have been completed.

Finally, number twelve is one that writers should do, and that’s …

12. Attend the 2020 Writers’ Police Academy/MurderCon. We have an unbelievably cool and over-the-moon exciting lineup in store for you. This is an event you will not want to miss!!

Honestly, we’ve outdone ourselves this year. We’ve been sitting on a few exciting secrets about the 2020 event and it’s almost time for the big reveal. So stay tuned, because we’ll soon be releasing the details.


MurderCon is moving forward as planned. We have carefully detailed plans in place for proper social distancing, and we’re furnishing masks. Hand sanitizer will be readily available.

Sirchie, our host, is in the loop with state and local health officials since they’re in the business of making PPE equipment, including hand sanitizer and masks, for 1st responders. Between Sirchie officials and our in-house microbiologist, Denene, we’re closely monitoring the situation and making preparations. Your safety, as always, is our priority.

Sign up today to reserve your spot!

MurderCon 2020

Regarding DNA and saliva, I’d like to note that it is indeed possible to expel DNA when coughing or sneezing. However, the fact that it’s possible doesn’t mean it’s always found, just that it could be. And, if found, it could be the DNA of someone other than than a suspect or victim, such as cop or lab scientist who was involved in the collection or testing of the evidence. Here’s why …

First, in the lab, to tell the difference between saliva and sputum, scientists look for epithelial cells. These cells have a nucleus, and within a nucleus DNA is found. Saliva is almost always present in the mouth, especially when we are awake. When we sneeze saliva and the DNA contained within is expelled.

FYI – Lab scientist/techs scan collected sputum samples for the presence or absence of white blood cells. White blood cells, not red, indicate infection. The presence of epithelial cells from saliva indicates the sample is contaminated with saliva, which would result in improper test results. Sputum is tested for respiratory tract infections. 

By the way, red blood cells (erythrocytes) have/contain no nucleus nor do they contain mitochondria. Therefore, red blood cells do not contain DNA because there’s no nucleus in the cells.

Those of you who attended the WPA when world-renowned DNA expert Dr. Dan Krane presented a fantastic session on DNA evidence, may remember when he mentioned how DNA evidence is sometimes contaminated, such as using fingerprint brushes or gloves from one scene to process evidence in an entirely different location. DNA could be transferred using those items. He also pointed out instances where coughing or sneezing could distribute DNA to the surface of an item being processed. (Dr. Krane is a former colleague of my wife, Denene)

On with DNA and Sneezing

As an example of evidence contamination via sneezing, when discussing the Jon Benet Ramsey case, Dr. Krane says, “The DNA in tests could be there because of a contact that was weeks, months, even years before the crime occurred. It’s not possible to make inferences about the tissue source here. We can’t say that it came from semen or saliva or blood or anything. What if one of the medical examiners sneezed on one of these articles of clothing and it came into contact with the other one? There are just so many possibilities.”

Additionally, from another source, “It is extremely easy to contaminate biological samples; this can occur by failing to change gloves or clean instruments properly, failing to wipe down benches properly between testing, or by sneezing or even talking over a sample (Buckleton et al 2005:277).”

And, from the National Institute of Justice:

Contamination

Because extremely small samples of DNA can be used as evidence, greater attention to contamination issues is necessary when identifying, collecting, and preserving DNA evidence. DNA evidence can be contaminated when DNA from another source gets mixed with DNA relevant to the case. This can happen when someone sneezes or coughs over the evidence or touches his/her mouth, nose, or other part of the face and then touches the area that may contain the DNA to be tested.

To avoid contamination of evidence that may contain DNA, always take the following precautions:

  • Wear gloves. Change them often.
  • Use disposable instruments or clean them thoroughly before and after handling each sample.
  • Avoid touching the area where you believe DNA may exist.
  • Avoid talking, sneezing, and coughing over evidence.
  • Avoid touching your face, nose, and mouth when collecting and packaging evidence.
  • Air-dry evidence thoroughly before packaging.
  • Put evidence into new paper bags or envelopes, not into plastic bags. Do not use staples.

From the U.S. National Library of Medicine/National Institute of Heath/The National Center for Biotechnology Information (NCBI):

4.2. Contamination

For DNA studies, one of the greatest laboratory barriers is the contamination of genetic material from other sources (e.g., from the examiner and other biological evidence). Contamination may occur during the sexual contact (e.g., if there is more than one perpetrator), during the period between the sexual contact and the FME, during the FME, and in the laboratory. In order to avoid it, examiners should take special precautions to prevent cross-contamination between evidences. For this purpose, it is important:

  1. to work under aseptic conditions to avoid microbial contamination;
  2. to always use disposable supplies to ensure individual protection (e.g., gowns, powder-free gloves, mask, or other protective clothing) and to avoid direct contact with the samples;
  3. to ensure that the room where FME takes place is regularly cleaned before and after patient use;
  4. to avoid sneezing, coughing, or talking over the samples;

Dr. Krane is one of the world’s foremost DNA experts, testifying worldwide as an expert witness in well over 100 criminal trials, in which DNA evidence was presented, such as the Jon Benet Ramsey case. He’s been involved as a top expert in other high-profile cases such as the DC Snipers, OJ Simpson case, and the infamous Monica Lewinsky/Bill Clinton “blue dress,” to name only a few. Dan also developed software that’s used in genetic analyzers, the devices used by scientists who conduct DNA tests.

My other source, in addition to our good friend Dr. Dan Krane, is, of course, my resident renowned expert, Dr. Denene Lofland.

Denene received a Ph.D. in Pathology, with an emphasis in microbiology, from Virginia Commonwealth University School of Medicine. As a former biotech company director, Denene managed successful clinical projects that resulted in regulatory filings of four compounds and FDA approval for two new antimicrobial drugs for the treatment of pneumonia and cystic fibrosis. The drugs are currently on the market.

Denene supervised several projects, including government-sponsored research which required her to maintain a secret security clearance. Her areas of expertise include medical microbiology, bioterrorism, and new drug discovery development. She has published numerous articles in a variety of peer reviewed scientific journals, contributed to the thirteenth edition of Bailey and Scott’s Diagnostic Microbiology, a textbook standard used in colleges and universities, published an article about anthrax in Police One magazine, and she has an upcoming tale in the Writers’ Police Academy’s anthology, After Midnight, Tales From the Graveyard Shift (edited by Phoef Sutton with foreword by Lee Child) ~ Level Best Books, publisher

Currently, Denene is an Associate Professor of Medical and Molecular Sciences at the University of Delaware. She also taught medical microbiology to medical students at a medical college in California. In her early days, prior to becoming a mad scientist, she managed the lab in a large, major hospital.

Over the years, I was fortunate to have the experience of witnessing Denene and her teams, and Dr. Krane’s team, perform numerous DNA testings using both gel electrophoresis and DNA Sequencers/Genetic Analyzers. I was once treated to conducting a test of my own in one of Dr. Dan Krane’s labs, an entire DNA test from extraction of sample to final result. I ran the test on the DNA of a strawberry, but hey, the process is the same as when using human samples. The strawberry was innocent, by the way.

Again, the fact that DNA is present in saliva, it doesn’t mean DNA is always found when someone sneezes or coughs, or talks over evidence (it’s even been found in traces of saliva found on a public phone receiver), just that it’s possible and that it does occur.


DNA Testing: The Process

The first step in the testing process is to extract DNA from the evidence sample. To do so, the scientist adds chemicals to the sample, a process that ruptures cells. When the cells open up DNA is released and is ready for examination.

extract-dna.jpg

DNA is actually visible to the naked eye. The slimy glob in the center of the circle below is DNA.

new-picture-11.jpg

DNA is tested in devices like the one below. They’re called genetic analyzers. This particular device is located in one of Dr. Dan Krane’s laboratories.

new-picture-1.jpg

DNA is loaded into wells inside the genetic analyzer. There are 96 wells in the gray, rectangular block shown below (inside the analyzer).

new-picture-2.jpg

An electric current separates the DNA, sending it from the wells through narrow straw-like tubes called capillaries. During its journey through the analyzer, DNA passes by a laser. The laser causes the DNA loci (a gene’s position on a chromosome) to fluoresce as they pass by, which allows a tiny camera to capture their images.

The image below shows DNA’s path through the genetic analyzer (wells are on the left; capillaries are the arcing lines leading to laser and camera on the right).

new-picture-3.jpg

Capillaries

new-picture-4.jpg

Doctor Stephanie Smith points to the row of eight capillaries, one for each well in the corresponding line of wells (12 rows of 8 wells).

At the end of the testing, the equipment produces a graph/chart called an electropherogram.

Peaks on the graph depict the amount of DNA strands at each location. It is this unique pattern of peaks and valleys that scientist use to match or exclude suspects.

Or, in the case of paternity testing, to include or exclude someone as a parent.

The image below is an electropheragram showing the DNA of a strawberry.

new-picture-8.jpg

Electropheragams are printed and it is this document that’s examined by experts for use in the ID/comparisons of sample contributors, such as suspects and victims.

Remember above when we discusses sneezing, coughing, and/or talking over DNA evidence? Well, here’s a DNA test result (electropheragram) of a contaminated sample, a mixture of DNA found on the body of a rape victim. The evidence was contaminated to the point that it was impossible to tell/prove whether or not Contributors 1 or 2 were involved in the assault. Notice that the peaks in the mixture do not quite match either suspect’s DNA.

Electropheragram showing tested DNA of two subjects, and a mixture of DNA collected from a victim. Results showing a mixture make it difficult to point to any one suspect, or if someone other than the suspect and victim contaminated the sample.

The image below shows a clear match between the DNA of the victim and suspect. The suspect was clearly in contact, in some way, with the victim.

 

DNA Facts:

Identical twins have identical DNA.

Humans are genetically 99.9% identical. Only 0.1% of our genetic makeup is different.

It takes about eight hours for one cell to copy its own DNA.

Red blood cells do not contain DNA.

DNA is used to determine pedigree in livestock.

DNA is used to authenticate wine and caviar.

Detergent and Alcohol will not destroy DNA.

DNA can be transferred from article of clothing to another, even in a washing machine. This is called secondary and tertiary transfer.

DNA testing is not 100% accurate.

*My thanks to Dr. Stephanie Smith and Dr. Dan Krane for allowing me to hang out in their labs to take the above photos.

*Thanks, too, to the good folks at crimescenewriter for the idea for this post. 


Have you reserved your spot at MurderCon? If not, there’s still time to do. Sign up today to attend this rare hands-on training event!

In the meantime, here’s a peek at the 2019 MurderCon instructors and speakers. The lineup is stellar!

MurderCon Instructors