RSS

Category Archives: DNA

Q and A: Can DNA Be Used To Identify Multiple Assailants In a Three Decade Old Rape?

Q: Was it possible in 1969 (or even today for that matter) to determine if a woman found dead in sub-zero temperatures was raped by more than one assailant. If so, how could this be accomplished? Could a pathologist conclude that the woman was raped, as opposed to consensual intercourse, even if there is an absence of physical evidence such as bruising? What language would the pathologist employ when writing his conclusions?  Could evidence from 1969 be preserved (how would it be preserved?) and used today to identified suspects through DNA testing?

D3

A: DNA for testing comes from the genetic material found in the nuclei of the body’s cells. Essentially every cell in the body contains a nucleus. The notable exception is the Red Blood Cells (RBCs), which do not contain nuclei. But, White Blood Cells (WBCs) do. DNA testing of blood tests the DNA found in the nuclei of the WBCs.

Adequate DNA samples for testing have been gleaned from semen stains, bite marks, sweat, sputum, hair, and saliva. Even from the saliva left behind by licking a stamp or sealing an envelope. In the case of saliva from stamps or bites, the DNA tested comes from the cells that line the mouth (called buccal cells), which are constantly shed into the saliva. Hair does not contain cells and thus no DNA, but hair follicles do. A single hair follicle may yield enough DNA for testing.

As you can see, very small samples might be enough.

DNA is a fairly hardy molecule and survives time, freezing, drying, mixing with other materials, and many other adverse circumstances. It does not survive heating, however. Heat denatures, or destroys, the DNA strands. It is important to note that DNA testing does not require intact cells, merely intact DNA. This means that clotted blood, dried semen, and tissue fragments found under victims’ fingernails might yield enough DNA for conclusive testing.

The sub-zero temperatures in your scenario would serve to protect the DNA and would thus help the coroner by preserving better samples for his evaluation.

Yes, he would be able to determine that there had been two assailants, since each would have his own distinctive DNA pattern. The finding of two different DNA patterns in the semen sample obtained from the victim would prove this and when the suspects were apprehended, each could be matched to his own contribution to that sample. Mixing the semen would not alter this finding in any way since each DNA strand would be unchanged. It’s not like mixing blue paint with yellow paint to make green paint but rather like mixing a bunch of tiny blue beads with tiny yellow beads. From a distance, they might appear as though they had melted together to form a green mixture, but on close examination, each tiny bead would be seen to have remained intact and separate. DNA strands don’t “melt” into one another.

DNA can last for years, decades, even centuries. It has been found in Egyptian mummies, exhumed bodies, and samples stored from very old crimes. Recently, DNA evidence linked Gary Leon Ridgway to the famous string of prostitute murders know as the Green River Murders in Washington State. The DNA evidence connected him to murders that occurred in the early 1980s. This was possible because the DNA was handled and stored properly. Typically, the sample is dried and placed in a non-reactive container such as a glass vial.

The problem of determining if a rape occurred is a question for the jury. Rape is not a medical term, but rather a legal term. The coroner could determine if penetration occurred and if semen was present. If he found trauma to the vagina or to other body parts that might suggest the victim was struck or restrained, he might conclude that in his opinion the intercourse was not consensual. Still, it would require a judge or a jury to determine whether a rape occurred or not.

Published in Suspense Magazine December, 2014

 

Murder Solved By Clever DNA Testing of an Old Stamp

DNA PROFILE

DNA PROFILE

Here is an amazing and convoluted story that involves good police work and clever DNA testing, including the use of old and very small samples and familial DNA techniques (instrumental in identifying the serial killer known as the Grim Sleeper). More proof that criminals can run but they can’t hide. Not for long anyway.

 

Want To See Something Very Small? DNA Replication Visualized

This is cool. You probably remember from high school biology that DNA copies itself as the first step in cell division. This is how we grow and how we replace lost or damages cells.

 

id37740

 

The replication process begins when the two strands of our double-stranded DNA “unzip.” That is, they split form one another. Then each stand rebuilds its complementary strand in a complex biological process. This yields two identical strands of double-stranded DNA, each of which becomes the nuclear material for the two identical cells when the division process is completed.

Current DNA analysis mirrors this natural phenomenon. State of the art DNA profiling employs the combination of the Polymerase Chain Reaction and Short Tandem Repeat analysis (PCR-STR). It’s the PCR portion that utilizes this natural process of replication, which is also called “amplification.”

Now it seems someone has used electron microscopy to visualize this process.

Amazing.

DNA Replication RCN.com: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/DNAReplication.html

You Tube: DNA Replication Video: https://www.youtube.com/watch?v=27TxKoFU2Nw

How Stuff Works: DNA Replication: http://science.howstuffworks.com/life/cellular-microscopic/dna3.htm

DNA Forensics: From RFLP to PCR-STR and Beyond: http://www.forensicmag.com/articles/2004/09/dna-forensics-rflp-pcr-str-and-beyond

 

 

Blue-eyed Mesolithic Caveman?

Was there an ancient Marlboro Man? Cool, swarthy. handsome?

DNA obtained from the wisdom tooth of the 7000-year-old remains of an European Mesolithic (Middle Stone Age) hunter-gather has been analyzed and suggests that the man had dark skin and hair, blue eyes, and was likely lactose intolerant.

Artist Impression of Mesolithic Hunter-gatherer

Artist Impression of Mesolithic Hunter-gatherer

We are all familiar with DNA’s use in solving crimes by matching a suspect to a crime scene and, particularly mitochondrial DNA (mtDNA), in ancestry investigations. DNA analysis can also often reveal sex, race, and hair and eye color.

Mesolithic Skull

Mesolithic Skull

Mesolithic Life in Europe Before the Curse of Farming: http://archaeology.about.com/od/mesolithicarchaic/qt/Mesolithic.htm

Historic Timeline: http://www.historiclandscape.co.uk/exploring_time.html

Stone Age Timelines: http://www.historiclandscape.co.uk/exploring_time.html

 
 

Jack The Ripper Identified?

article-2746321-21208C4300000578-24_634x485

 

A new book titled Naming Jack The Ripper by Russell Edwards presents information that the author feels solves the famous Jack The Ripper case. The five murder-mutilations that occurred in London’s East End during 1888 have baffled criminologists for over a century. Several suspects have been identified but none have been proven to be the real Ripper. So who is Jack? According to Edwards, it’s Aaron Kosminski, a Polish immigrant who had “mental issues,” was 23 years old at the time of the killings, and who ultimately died in an insane asylum many years later at the age of 53. He never confessed or anything convenient like that, but he has long been one to the prime suspects.

So is he really Jack? Maybe. Here are some articles. Make up your own mind.

Daily Mail UK: http://www.dailymail.co.uk/news/article-2746321/Jack-Ripper-unmasked-How-amateur-sleuth-used-DNA-breakthrough-identify-Britains-notorious-criminal-126-years-string-terrible-murders.html

Independent UK: http://www.independent.co.uk/news/science/has-jack-the-rippers-identity-really-been-revealed-using-dna-evidence-9717036.html

Mirror UK: http://www.mirror.co.uk/news/uk-news/jack-ripper-murder-mystery-solved-4177665

 

Jack-the-Ripper-shawl-4

 

Crime and Science Radio: Taking A Bite Out Of Crime: An Interview with Forensic Dentist Dr. Michael Tabor

Join Jan Burke and DP Lyle as they explore the world of forensic dentistry with Dr. Mike Tabor, Chief Forensic Dentist of the State of Tennessee Office for the Medical Examiner. Learn exactly how forensic dentistry aids in corpse identification and dig into some of Dr. Tabor’s most famous cases.

 

MTabor

 

BIO: In the spring of 1973, Mike Tabor embarked on a journey that would take him down a path he could have never imagined. With a freshly earned DDS, Dr. Mike Tabor left Carson-Newman College and The University of Tennessee College of Dentistry, and began his career as a family dentist. In 1983, Dr. Tabor’s work as a family dentist took a unique turn and he found himself immersed in the highly specialized field of forensic dentistry. As one of only a handful of forensic dentists in the United States, Dr. Tabor became a highly sought after expert in this field, performing identifications and examinations on homicide victims, as well as aiding police departments, investigators and medical examiners all over the Country in the prosecution of thousands of crimes.

In September of 2001, Dr. Tabor found himself in New York, at the site of the World Trade Center terror attacks, aiding in the identification of countless victims. For Mike Tabor, this infamous and historical event forever changed his life. As a forensic dentist, Mike was no stranger to the examination of deceased victims, but the horrors of September 11th would not allow Mike, the man, to separate himself from his work as Dr. Tabor, the forensic dentist. September 11, 2011 left a lasting and emotional impression on Mike and gave him a completely new perspective on life and loss.

Dr. Mike Tabor was a featured contributor and has written an entire chapter for the Internationally Accredited Textbook, Forensic Dentistry. He has served as the president of the Tennessee State Board of Dental Examiners, and is currently the Chief Forensic Dentist for The State of Tennessee Office of the Medical Examiner, and is an energetic, engaging and highly respected and sought after public speaker. He makes his home in Nashville, with his beautiful wife, Karen and their two snow white canine children, Mollie and Millie. He is the proud father of two grown children and the doting grandfather of seven adorable grandchildren.

LISTEN: 

LINKS:

Dr. Michael Tabor’s Website: http://www.drmiketabor.com

Dr. Michael Tabor’s Blog: http://www.drmiketabor.com/blog/

Walk Of Death: http://www.amazon.com/Walk-Of-Death-Forensic-Novel/dp/1490533737

American Society of Forensic Odontology: http://asfo.org

How Stuff Works: Forensic Dentistry: http://science.howstuffworks.com/forensic-dentistry.htm

Forensic Odontology: http://www.nlada.org/forensics/for_lib/Documents/1124743291.01/425lect16.htm

International Association for Identification: http://www.theiai.org/disciplines/odontology/

Forensic Dentistry Online: https://www.forensicdentistryonline.org

Medscape: Forensic Dentistry: http://emedicine.medscape.com/article/1771750-overview

Wikipedia: Forensic Dentistry: http://en.wikipedia.org/wiki/Forensic_dentistry

Forensic Dentistry Careers: http://criminologycareers.about.com/od/Forensic-Science-Careers/a/Career-Profile-Forensic-Odontologist.htm

Animal and Human Bite Mark Analysis: http://www.forensic.to/webhome/bitemarks/

Crime Library: Bite Marks As Evidence: http://www.crimelibrary.com/criminal_mind/forensics/bitemarks/1.html

Writers Forensics Blog: Guest Blogger: Dr. Mike Tabor: Anatomy Of A Forensic Dental Identification: https://writersforensicsblog.wordpress.com/2014/06/05/guest-blogger-mike-tabor-anatomy-of-a-forensic-dental-identification/

 

WalkofDeath

 

Guest Blogger: Daphne Holmes: How DNA Testing Helps Determine Paternity

DNA

 

How DNA Testing Helps Determine Paternity

The impetus for determining the paternity of a child likely dates back to the most primitive tribal cultures. Particularly in patriarchal cultures where females were regarded as the property of males, it was deemed important to ensure that a man’s “property” had not been shared, and that the virtue of the female was beyond question. As societies became more sophisticated, the need to establish paternity became as much an economic issue as a moral one. In modern cultures, paternity testing is used primarily to establish whether or not a man is responsible for providing financial support to a child, as well as determining whether the child carries any of the father’s genetic predispositions for health challenges.

Physical appearance – In more primitive cultures (some of which continue to flourish), the objectives behind determining the paternity of a child were culturally and/or emotionally based. If a child was born who lacked identifying characteristics of either parent, it was frequently assumed that the father was someone other than the woman’s mate. The repercussions to the mother were quite severe, often culminating in her death. Unfortunately – especially for the women – the comparison of obvious physical traits was highly subjective, and many women suffered dire consequences, even if their husband/mate was indeed the biological father.

Blood typing – With the early 20th century discovery that different individuals had different blood types, and the recognition in the 1920s that those blood types were genetically inherited, a more accurate means of determining paternity came into common use. It was discovered that by comparing the parents’ blood types, it was possible to determine the most likely blood type of the child. While this was admittedly a step above the “he has his father’s eyes” paternity test, it was still only about 30% accurate.

Serological testing – It was discovered in the 1930s that specific proteins not considered during blood typing could establish the presence of genetically inherited antigens that would more accurately identify the child’s biological father. Unfortunately, serological testing only improved the accuracy of paternity testing to about 40%. Hardly conclusive evidence.

Tissue typing – In the 1970s, the human leukocyte antigen (HLA) was discovered in abundance within white blood cells. When samples of this genetically inherited antigen taken from the mother and child were compared to the sample taken from the father, paternity could be established with roughly 80% accuracy. While this was a significant improvement over previous methods, the collection procedure itself was unpleasant, and the size of the sample required made it hazardous to the child, particularly if the child was less than six months old. Obviously, more work needed to be done.

DNA testing (RFLP) – In the 1980s, the technique called restriction fragment length polymorphism (RFLP) was discovered that looked at a significantly wider spectrum of variables in the blood than had been analyzed with earlier techniques. It was discovered that the offspring of two parents would have half the unique characteristics of each parent. This technique elevated the accuracy of paternity testing to the level of statistical certainty. Unfortunately, the amount of blood required for accurate sampling was, like tissue sampling, large, posing potential problems for the child. In addition, the potential for genetic mutations in the child could render a false negative, indicating that neither the woman or the man was the child’s biological parents. For these reasons, RFLP testing has been all but abandoned.

DNA Testing (PCR) – By the 1990s, the RFLP testing was replaced by the polymerase chain reaction (PCR) technique. This technique involves the computerized replication of DNA collected from even a minuscule sample that is collected anywhere on the individual’s body, then comparing the subjects’ profiles. In addition to requiring a very small sample (typically via an oral swab), the subject is not submitted to discomfort as in earlier test techniques, and the computerized analysis takes far less time, while still providing accuracy at the level of statistical certainty, 99.99%.

Author: Daphne Holmes contributed this guest post. She is a writer from www.ArrestRecords.com and you can reach her at daphneholmes9@gmail.com.

 

 
 
Follow

Get every new post delivered to your Inbox.

Join 2,390 other followers