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Category Archives: General Forensics

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?

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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.

 

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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

 

 

Fingerprint Lifting in Adverse Conditions

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Adverse. environmental conditions are there bane of forensic investigators. Heat, cold, humidity, rain, snow, you name it, can alter, damage, and destroy corpses, trace evidence, blood and other bodily fluids, DNA, and, of course, fingerprints. It requires tricks of the trade to sniff out the evidence under such circumstances.

Here is an interesting article on handling fingerprints when the day isn’t sunny and bright.

 

 

 

 

Crime and Science Radio: Improving Forensic Science With Kevin Lothridge Of The NFSTC

Saturday, November 15, 2014, at 10 a.m. Pacific: Crime and Science Radio: Improving Forensic Science: An Interview With Kevin Lothridge Of The NFSTC

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Join Jan Burke and I as we welcome Kevin Lothridge, CEO of the National Forensic Science Technology Center, an organization that has developed protocols for educating forensic science professionals and improving and standardizing the varied fields of forensic investigation.

BIO: Kevin Lothridge, Chief Executive Officer – NFSTC’s principal investigator, Mr. Lothridge is an accomplished forensic scientist and business leader with 28 years of experience in the international forensics industry. He has held positions as a forensic chemist, chief forensic chemist, and laboratory director for the Pinellas County Sheriff’s Department and the Pinellas County Forensic Laboratory. Mr. Lothridge has testified in court more than 50 times as an expert in controlled substances and fire debris analysis. He speaks at numerous professional conferences, and he co-authored the GC-MS Guide to Ignitable Liquids. In 2006-07, he led the development of the Expeditionary Analysis Center project for the Department of Defense, now used for training and tactical field forensics.

Mr. Lothridge holds a bachelor’s degree in Forensic Science from Eastern Kentucky University and a master’s degree in Management from National Louis University. He has served as president of the American Society of Crime Laboratory Directors (ASCLD) and as acting chief of the Investigative and Forensic division of the National Institute of Justice (NIJ).

General NFSTC description:

The National Forensic Science Technology Center (NFSTC) is a 501(c)(3) not-for-profit corporation headquartered in Largo, Florida. Founded in 1995, NFSTC provides quality forensic services including biometrics and forensic science training, assessment, test and evaluation services, instructional design and support to the military, justice and forensic science communities.

LISTEN:

http://www.blogtalkradio.com/suspensemagazine/2014/10/16/crime-and-science-radio-with-special-guest-kevin-lothridge

LINKS:

National Forensic Science Technology Center: http://www.nfstc.org

Forensic Science Simplified: http://www.forensicsciencesimplified.org

NFSTC on Facebook: https://www.facebook.com/nfstc

NFSTC on Twitter: https://twitter.com/nfstc

NFSTC on LinkedIN: https://www.linkedin.com/company/national-forensic-science-technology-center—nfstc

NFSTC Instructional Videos on Youtube: www.youtube.com/thenfstc

NamUs, the National Missing and Unidentified Persons System: http://www.namus.gov

 

Greed Can Be Dangerous: A 2800-year-old Case Solved?

Gold Bowl

 

How did a valuable gold bowl and three skeletons end up at the bottom of a refuse shaft in the ancient Iranian citadel of Hasanlu? It just might have been a building collapse that did in the unlucky thieves. Interesting historical forensics.

New Scientist: http://www.newscientist.com/article/dn26129-iron-age-csi-finds-gold-thieves-died-in-the-act.html?full=true&print=true#.VAS4ekuaGzA

Ancient Origins: http://www.ancient-origins.net/news-general/dark-tale-behind-golden-bowl-hasanlu-002054

 

Remains of the citadel of Hasanlu

Remains of the citadel of Hasanlu

 

Fingerprinting Bullets: A New Forensic Science Technique

Bullets recovered from crime scenes or bodies can tell investigators a great deal: the caliber of the weapon can be determined by measuring and/or weighing the bullet; the marks left on the bullet’s surface by the lands and grooves and twists of the barrel can reveal the manufacturer; and these same striations can be used to match the bullet to a particular suspect weapon. These striations area the most individualizing and therefore the most useful in criminal investigations involving forearms.

But what if the bullet is too damaged for such comparisons? All is not lost. An analysis of the chemical make up of the bullet might reveal not only the manufacturer but also the batch from which it came. This might serve to narrow the location of purchase and ultimately lead to the perpetrator..

Bullet Fingerprints To Help Solve Crimes: http://phys.org/news/2014-07-bullet-fingerprints-crimes.html

 
 
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