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Category Archives: DNA

Bugging Your DNA

Mosquito

 

Everybody hates mosquitoes. They irritate, they bite, and they carry disease. In fact they are likely the most deadly creature on Earth since they spread malaria through many regions of the world. They also spread things like yellow fever and Zika – – – and a host of other nasty little problems.

But can mosquitoes place you at a crime scene? If so, how would this work?

Let’s say investigators come to a murder scene and find a smashed and dead mosquito on the bed sheets near the corpse. It might be reasonably assumed that this mosquito bit someone and that person then killed it, leaving it where it fell. Could that be used to ID the killer?

It appears that human blood can remain in the mosquito’s stomach for up to two days. And if this is extracted, it can be used in DNA profiling. So the mosquito at the crime scene could be collected and tested, and if DNA were found, a profile could be generated and lead back to the killer.

Esoteric, but fascinating.

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14 Comments

Posted by on August 31, 2017 in Crime Scene, DNA, High Tech Forensics

 

DNA Solves the 80-Year-Old Death of Belgium’s King Albert I

Belgium-Albert-King-of

 

Belgium’s King Albert I was found dead on February 17, 1934. The experienced rock climber was found at the base of a large formation with a gash to his head. Speculation that he was murdered ran rampant. During World War I, he had resisted Germany and attempted to block German troops from entering his country. They eventually did, but he fought them every step of the way. Was Germany somehow complicit in his untimely death?

Many felt that he had been killed elsewhere and his body dumped where it was found. The evidence suggested otherwise. His glasses were found nearly 40 feet above him – – he was very far-sighted – – and his climbing rope was still attached to his body. But, the most important evidence that suggested a fall rather than a murder was blood on the leaves near the King. If this blood was indeed Albert’s, then he must have shed it at that location, meaning he was at least briefly alive when he reached the ground at the base of the rock formation. If he had been killed elsewhere and dumped, there would have been no blood around the body. Dead folks don’t bleed. The leaves were apparently collected and preserved.

Flash forward to 2014. The blood of the leaves was tested. Not only was it human blood and but also it was matched against two relatives of the King. These results suggested that the blood was indeed the King’s blood and it had likely been shed from a head injury he received from his fall. This 80-year-old “murder” case seems to be a tragic accident.

 

Q&A with Expanded Audio Discussions Now on the Suspense Magazine Website

Q&A with Expanded Audio Discussions Now on the Suspense Magazine Website

Check out the new posts John Raab of Suspense Magazine and I put together. Read the Q&As and listen to the expanded discussions. Hope each proves helpful for your crime fiction.

Can DNA Be Used To Identify Multiple Assailants In a Three Decade Old Rape?

http://suspensemagazine.com/blog2/2016/12/20/d-p-lyles-forensic-file-episode-1/

In 1863, Could An Autopsy Accurately Determine the Cause of Death?

http://suspensemagazine.com/blog2/2017/01/09/in-1863-could-an-autopsy-accurately-determine-the-cause-of-death-d-p-lyle-answers-this/

Can My Female Character Cause Her Pregnancy To Become “Stone Baby” By Shear Will?

http://suspensemagazine.com/blog2/2016/12/31/can-my-female-character-cause-her-pregnancy-to-become-stone-baby-by-sheer-will/

More to come.

Want more cool questions from crime writers? Check out my three Q&A books.

M&M 200X300

More Info and List of Included Questions

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More Info and List of Included Questions

MF&F 200X320

More Info and List of Included Questions

 

Father’s Unborn Twin Is the Genetic “Father” of His Son

A couple of years ago a happy couple in Washington welcomed a new baby boy. All was good until a paternity test showed that the father was not the father. Uh-oh. Well, it’s not really that bad. Turns out that genetic testing revealed the father was a chimera and the genetic testing was confused by his unborn twin’s DNA, which the father had absorbed in utero. Chimerism is an odd and interesting medical entity.

 

Greek Chimera

In Greek Mythology, the Chimera was a fire-breathing female that was part lion, part goat, and part dragon. Fortunately, human chimeras, which result from the combining of two or more human embryos in utero, are typically normal in every way—-except for that DNA stuff.

I’ve blogged and had Guest Bloggers comment on chimeras before:

Q&A: How Could My Sleuth Recognize a Chimera?

https://writersforensicsblog.wordpress.com/2010/07/05/qa-how-could-my-sleuth-recognize-a-chimera/

Guest Blogger: EE Giorgi: I Am My Mother’s Chimera. Chances Are, So Are You

https://writersforensicsblog.wordpress.com/2014/04/09/guest-blogger-ee-giorgi-i-am-my-mothers-chimera-chances-are-so-are-you/

Guest Blogger: Human Chimerism: Mindboggling DNA Tests Gone Wrong

https://writersforensicsblog.wordpress.com/2010/06/24/human-chimerism-mindboggling-dna-tests-gone-wrong-guest-blogger/

http://www.people.com/article/man-fails-paternity-test-twins-genes

 

Can a DNA Sample Reveal Age?

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DNA found at crime scenes can be extremely useful in identifying a perpetrator. But this only works if they have a known suspect and a DNA sample from that suspect, or if the perpetrator is in the national DNA database—-CODIS. Without something to compare the crime scene DNA sample against, DNA is not very useful. Same can be said for fingerprints. But perhaps DNA offers something else.

Employing DNA obtained from a crime scene, Familial DNA has been used to narrow the list of potential suspects and this has proven useful in many cases—such as the famous Grim Sleeper serial killer. I have blogged on this before in cases such as The Boston Strangler and the amazing case of Yara Gambirasio.

DNA will of course reveal gender, but there is also research suggesting that race, hair and eye color, and physical features such as stature might also be determined from a DNA sample. These aren’t completely worked out yet but they are intriguing aspects of DNA analysis.

But what if a DNA sample could be used to determine the approximate age of the person? This would definitely help as, once again, it would narrow the suspect list. For example, if the crime scene DNA could be shown to have come from someone who was approximately 25 years old it would effectively eliminate a 60-year-old suspect. But is this possible? Maybe.

A new approach, using a process of gene expression called methylation, seems to offer hope. Researchers at the KU Leuven University in Belgium have developed a technique for assessing the degree of methylation in a DNA sample. They believe that this analysis will narrow the age range of the individual down to a four or five year window. If this proves to be true, law enforcement will have another useful forensic science tool.

 

Even Identical Twins Have Different DNA

For years the dogma was that identical twins possessed DNA profiles that were not distinguishable from one another. But things are changing.

Fraternal (dizygotic) twins come from two eggs and two sperm and are as different as if born years apart. They are twins solely because they shared the mother’s womb at the same time. But, identical twins (monozygotic) come from a single egg and sperm. They are formed when the fertilized egg undergoes its first division and the two new daughter cells move apart, each then proceeding to form a separate individual. Since they came from the same fertilized egg, the share the same DNA. In fact, the two would be indistinguishable by standard PCR-STR DNA Profiling.

 

Twins

 

But, in reality, even identical twins have distinct DNA. We just weren’t able to see the differences. Before now.

As each twin embryo grows and develops in utero, and the cells continue to multiply, the replication (copying) of each twin’s DNA isn’t perfect. Minor errors or variations begin to appear so that by birth each Twin’s DNA is slightly different from its sibling. And as life goes on, each twin is subjected to different environmental stresses, which is turn alters each one’s DNA replication.

As opposed to STR, which looks at repeating short sequences of bases within the DNA strand, a newer DNA technique, known as Single Nucleotide Polymorphism (SNP), gives the examiner a complete DNA sequence of the strand being analyzed. That is the exact sequence of bases in each strand is determined and this can reveal the differences in the DNA of identical twins. Another newer technique known as High Resolution Melt Curve Analysis (HRMA) might offer still another method to make this distinction.

So even identical twins are not so identical.

Want to know more about DNA profiling? Check out the updated 2nd Edition of FORENSICS FOR DUMMIES.

 

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2 Comments

Posted by on May 2, 2016 in DNA, Uncategorized

 

Guest Blogger: Lisa Black: Everything Old Is New Again

EVERYTHING OLD IS NEW AGAIN

My character, Cleveland forensic specialist Maggie Gardner, is unrealistic in one respect—she still spends a lot of time at her microscope looking at tiny bits of trace evidence, hairs, fibers, paint, and glass.

No one does that any more. Well, maybe Abby on NCIS, but she’s the most unrealistic forensic person on screen, even though she’s so cute we don’t care.

Sure, on old episodes of Dragnet you can see some nerdy guy in a lab coat explain how these pollen spores are only found in one quadrant of the city, but that art had already died before I started in forensics in 1994. We got spoiled by DNA, by ‘absolutely yes’ or ‘absolutely no’ answers. No one wanted to hear that this red nylon was ‘consistent with’ the suspect’s shirt, because they wouldn’t be hearing how many red nylon shirts were manufactured, how many were sold in this area, and while we’re at it let’s hack into Macy’s sales figures and find out who they were sold to. Unlike television, forensic labs do not have databases of all this information and would probably be violating a few important laws if they did. Nope, ‘consistent with’ was all you got. Take it or leave it.

 

Polyurethane_Fibers

POLYURETHANE FIBERS

They left it. Microscopic analysis became more or less a thing of the past. Forensic techs today wouldn’t recognize a pollen spore or know what to do with it if they did. Fibers are ignored. Hairs are examined only to screen out candidates for, well, DNA.

Imagine my surprise, then, when I peruse the latest Journal of Forensic Sciences and stumble on an article about using something called palynological scanning to rapidly evaluate suspect and victim testimony.

 

pollen

POLLEN

Palynology, it turns out, is a fancy name for…pollen. Pollen and spores and other ‘microscopic entities’ of trees, shrubs and herbs. No hairs, fibers or paint, but you get the idea. This analysis proved useful in some cases of rape or assault, in situations where the victim and suspect both contacted the ground and pieces of the ambient flora could attach to their clothing.

 

trees

 

In one case the suspect said he and his victim engaged on a lawn behind a public building. The victim said he attacked in a heavily wooded area, the spot surrounded by beech, birch and sycamore trees. Each site had a distinct mix of items—palynomorphs– with complicated Latin names. The suspect didn’t deny that he had made contact with the victim so willingly gave up the clothing he’d been wearing at the time, and sure enough, all those little palynomorphs indicated that he had been in the woods and not on the lawn. This did not prove that he had committed the crime. It only proved that he had lied about the sequence of events, and that was sufficient to prompt a confession. Otherwise this case would have languished in an eternal hell of ‘he said vs. she said.’

Of course had this guy listened to legal counsel before he made a statement, he probably would have figured out to come up with an alternative, and innocent, reason to have been rolling on the ground near the crime scene, and all these spores would have been for naught. As it is, surely the defense will bring out statistics regarding the vast number of beech and sycamore trees in the area, perhaps in the suspect’s own neighborhood, and the idea that maybe he had been doing some gardening earlier in the week in that same pair of pants. This is why things like pollen analysis fell out of favor with the courts…but the spores are still out there, voluminous, distinct and quite concrete little buggers that will stick in all sorts of places one might wish they wouldn’t. So are hairs, fibers, and paint. Maybe ‘consistent with’ is all you can get out of them. But maybe, sometimes, that’s enough.

So in my books Maggie still looks at all this stuff because it’s more visible and visceral than yet one more DNA sample. Let’s face it—you’ve seen one cotton swab, you’ve seen them all. Bright clothing fibers are much more entertaining.

And this trace evidence will lead her down a number of roads—some of which, it turns out, she’d be better off avoiding.

Wiltshire et al. “A Rapid and Efficient Method for Evaluation of Suspect Testimony: Palynological Screening.” Journal of Forensic Sciences, Vol. 60, #6, Nov 2015, pp 1441-1450.

 

L Black

Lisa Black has spent over 20 years in forensic science, first at the coroner’s office in Cleveland Ohio and now as a certified latent print examiner and CSI at a Florida police dept. Her books have been translated into 6 languages, one reached the NYT Bestseller’s List and one has been optioned for film and a possible TV series.

Lisa’s Website: http://www.lisa-black.com

 

that darkness cover

 

Hello! Just a quick note to let you know that my new book, That Darkness, is now available wherever books are sold!

It seemed like a typical week for crime scene specialist Maggie Gardiner–a gang boss shot in an alley, a lost girl draped over an ancient grave, a human trafficker dumped in the river–nothing all that out of the ordinary for the Cleveland police department as spring turns toward summer along the Erie banks. The methods are usual, the victims unsurprising–but when she notices a pattern, a tenuous similarity among the cases, she begins to realize that her days will never be typical again. How much of her life, her career, her friends, will she be willing to risk to do what’s right?

Jack Renner is a killer who does not kill for any of the conventional reasons…no mania, no personal demons. He simply wants to make the world a safer place. He doesn’t think of himself as a dangerous person–but he can’t let anyone stop him. Not even someone as well-meaning as Maggie Gardiner.

Maggie has the self-sufficiency of a born bit-of-a-loner. She works with a bevy of clever experts surrounded by armed police officers. She is both street smart and book smart, having seen the worst the city has to offer.

But Maggie Gardiner is not safe. And, until she can draw Jack Renner into the light, neither is anyone else.

Jeff Lindsay, author of the Dexter series, says: “Lisa Black always delivers authentic characters in riveting stories. That Darkness takes things to a spellbinding new level with a taut and haunting story that will stay with you long after you finish reading it.”

Publisher’s Weekly says: “The intriguing forensic details help drive the plot to its satisfying conclusion.”

“Black is one of the best writers of the world of forensics, and her latest introduces Maggie Gardiner, who works for the Cleveland Police Department. Her relentless pursuit of answers in a dark world of violence is both inspiring and riveting. Readers who enjoy insight into a world from an expert in the field should look no further than Black. Although Cornwell is better known, Black deserves more attention for her skillful writing – and hopefully this will be her breakout book.”– RT Book Reviews, 4 Stars (Top Pick)

 
 
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