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Category Archives: Crime Scene

Assessing The Crime Scene in 3D

Crime scene documentation is a critical step in criminal investigations. Knowing the spatial relationships between perpetrator, victim, and evidence items such as weapons, shoe prints, blood spatter, etc., as well as the physical layout of the scene, affords investigators a better look at who did what to whom. For many years, crime scene sketches, photos, and videos have proven useful in this regard.

Such techniques are discussed in detail in my book HOWDUNNIT: FORENSICS

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But wouldn’t a 3D holograph of the scene offer an even better understanding? Wouldn’t it be useful to “show” jurors how the crime actually went down? Looks like that might now be possible.

The process begins with laser mapping of the scene:

CS Laser

As stated by Jeremy Bailenson of the Virtual Human Interaction Lab at Stanford University in California: ”Imagine you could transport the entire jury, the judge, the litigators – everybody – back to the crime scene during the crime.”

Yeah. Imagine that.

 

Toilet Paper to the Rescue

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“I have a gun. Give me $300.”

Here’s a bit of advice: If you plan to rob a bank or a business, say a pizza joint, don’t write your “stick up” note on toilet paper and then leave the roll behind for the police to find when they search your home. If you do, you give the investigators much to work with in connecting you to the crime. Don’t believe me? Ask Eric Frey.

In this case, Frey left behind “indented writing” on the roll and, much to his dismay, investigators were able to match this “writing” that that on the note.

This is definitely an odd case of Forensic Document Examination.

Two other forensic techniques that could enter the picture here would be chemical ink analysis and fracture pattern assessment. The ink on the note could be chemically matched to the marker pen found at Frey’s residence and this could serve to further link him to the note.

Also, since no two things fracture, crack, or tear the same way, analysis of the torn edges could match the note paper to the roll—-if no other tissues had been torn away after the note was removed. The tear line between the roll and the note paper would match and this match is about as good as DNA or fingerprints. Such tears, like broken glass or chipped paint or broken sticks, are called fracture patterns and they are highly individual.

There is an entire chapter on the fascinating field of Document examination in my forensic books Howdunnit: Forensics and Forensics For Dummies.

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And a few links for you to explore:

A Simplified Guide to Forensic Document Examination: http://www.forensicsciencesimplified.org/docs/how.html

FBI Forensic Ink Analysis: http://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/july2005/research/2005_07_research02.htm/

Glass Fracture Patterns: https://www.ncjrs.gov/pdffiles1/nij/grants/241445.pdf

Howdunnit:Forensics and my other Forensic Books: http://www.dplylemd.com/DPLyleMD/Books-Forensics.html

 
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Posted by on February 24, 2015 in Crime Scene, Document Examination

 

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.

 

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.

 

 

 

 

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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