RSS

Category Archives: crime lab

Does Your DNA Contain Your Image?

DNA-Based Sketches

 

To say that DNA had revolutionized criminal investigations would be a huge understatement. Prior to DNA profiling, identifying a suspect with absolute certainty was more difficult. Fingerprints would work, of course, and eyewitness accounts, though flawed in many ways, could also help. But a criminal leaving behind biological evidence such as blood, semen, saliva, hair, skin cells, and other little bits, offers a method of identity that is second to none. DNA profiling has been used to catch many a criminal. But, in order for it to do its work, there must be something for the DNA analyst to compare the crime scene sample against. The DNA database, CODIS, helps because it stores millions of DNA profiles and if the perpetrator is in the system, a match can be made. But if he is not, the database is of little help.

DNA analysis can reveal the gender of the person who left behind the sample quite easily. But our DNA controls more than that. It determines how tall we will be, what our hair and eye color will be, our intellectual level, our ability to play music, and many other things. Familial DNA has been used to narrow down unknown samples to a smaller group, such as an extended family. And lately, this is been used in conjunction with the various ancestral databases to solve some crimes. But a newer technique offers another tool on the DNA front. It’s called DNA Phenotyping.

The principle seems simple: Since our DNA determines what we look like, would it not be possible to take a DNA sample and then create an image of the individual it belonged to? Maybe. At least great strides have been made in that regard. A case in point is that of research biologist Le Bich-Thuy, who was raped, battered, and strangled 24 years ago. DNA obtained from that scene was subjected to DNA Phenotyping and an image of the individual who likely perpetrated the crime was generated. Not only that, the image was age altered so that it would more accurately reflect what he might look like now. Fascinating case.

Advertisements
 

Improved GHB Testing

nmr

NMR Spectrograph

GHB is one of the so-called Date Rape Drugs—along with Ecstasy, Rohypnol, and Ketamine. I have an article on these on my website (See Below).

GHB has been difficult to detect, primarily because it’s rapidly metabolized (destroyed) by the body. But new techniques employing Nuclear Magnetic Resonance (NMR) Spectroscopy allow the detection of GHB metabolites (breakdown products) as much as 24 hours later. This gives investigators a longer time period to uncover GHB in a victim.

GHB can also often be found in the victim’s hair up to a month or more after exposure, but this testing is not as yet perfected.

https://www.forensicmag.com/news/2017/08/chemists-discover-marker-date-rape-drug-testing

http://www.dplylemd.com/articles/date-rape-drugs.html

https://www.ncbi.nlm.nih.gov/pubmed/25433016

More on the fascinating world of Forensic Toxicology can be found in FORENSICS FOR DUMMIES:

http://www.dplylemd.com/book-details/forensics-for-dummies.html

FFD 300X378

SaveSave

 

Holmes, Thorndyke, Locard, Gross, and the Modern CSI

There are no bigger names in the history and development of modern crime scene investigation than French investigator Edmond Locard and his Austrian counterpart Hans Gross. These two men shaped the development of crime scene investigation and even today their techniques create the cornerstone of forensic science. Locard’s Exchange Principle underlies every forensic technique.

locard1

EDMOND LOCARD

hans-gross

HANS GROSS

They were also great fans of Sir Arthur Conan Doyle’s Sherlock Holmes and R. Austin Freeman’s Dr. John Evelyn Thorndyke. Locard even suggested that students of police procedure read the Sherlock Holmes stories and learn from his techniques.

Sherlock_holmes_paget_slider

Both the real-life investigators and the fictional ones had one thing in common: the careful and meticulous approach to any crime scene, taking care to collect all useful evidence, while not damaging or contaminating it.

In my book Forensics For Dummies, the methods and techniques used to evaluate a crime scene and collect evidence are explained in great detail. Check it out if you want to know more about the techniques that saw their origin more than 100 years ago.

FFD 300X378

 

The Queen of Poisons and The Marsh Test

ii_b_114c

Arsenic has, over the centuries, garnered many colorful names. It was called the “queen of poisons” because it was so readily available, easy to use, highly effective, and untraceable. Thus, it was used by many famous historical poisoners. Some called it the “king of poisons” but since over the years,  female killers have favored poisons, “queen” seems more apt. It was also called “inheritance powder,” for obvious reasons—-once the estate holder is dead and gone, the heirs can party down.

Arsenic is the nearly perfect poison. This was definitely true centuries ago when there was no way to trace it. But what about today, with modern toxicological techniques? Unfortunately, arsenic is still a pretty good choice for the poisoner. It’s not often looked for in unexplained deaths and its effects mimic many medical conditions, particularly neurological and gastrointestinal.

Back a couple of centuries ago, because of its common use, a method for finding arsenic in the dead or ill became an imperative. There were many steps along this path. This search for arsenic was essentially the beginning of forensic toxicology.

From HOWDUNNIT: FORENSICS

Arsenic had been a common poison for centuries, but there was no way to prove that arsenic was the culprit in a suspicious death. Scientists had to isolate and then identify arsenic trioxide—the most common toxic form of arsenic— in the human body before arsenic poisoning became a provable cause of death. The steps that led to a reliable test for arsenic are indicative of how many toxicological procedures developed.

1775: Swedish chemist Carl Wilhelm Scheele (1742–1786) showed that chlorine water would convert arsenic into arsenic acid. He then added metallic zinc and heated the mixture to release arsine gas. When this gas contacted a cold vessel, arsenic would collect on the vessel’s surface.

1787: Johann Metzger (1739–1805) showed that if arsenic were heated with char- coal, a shiny, black “arsenic mirror” would form on the charcoal’s surface.

1806: Valentine Rose discovered that arsenic could be uncovered in the human body. If the stomach contents of victims of arsenic poisoning are treated with potassium carbonate, calcium oxide, and nitric acid, arsenic trioxide results. This could then be tested and confirmed by Metzger’s test.

1813: French chemist Mathieu Joseph Bonaventure Orfila (1787–1853) devel- oped a method for isolating arsenic from dog tissues. He also published the first toxicological text, Traité des poisons (Treatise on Poison), which helped establish toxicology as a true science.

1821: Sevillas used similar techniques to find arsenic in the stomach and urine of individuals who had been poisoned. This is marked as the beginning of the field of forensic toxicology.

1836: Dr. Alfred Swaine Taylor (1806–1880) developed the first test for arsenic in human tissue. He taught chemistry at Grey’s Medical School in England and is credited with establishing the field of forensic toxicology as a medical specialty.

1836: James Marsh (1794–1846) developed an easier and more sensitive version of Metzger’s original test, in which the “arsenic mirror” was collected on a plate of glass or porcelain. The Marsh test became the standard, and its principles were the basis of the more modern method known as the Reinsch test, which we will look at later in this chapter.

As you can see, each step in developing a useful testing procedure for arsenic stands on what discoveries came before. That’s the way science works. Step by step, investigators use what others have discovered to discover even more.

I ran across an excellent article on the Marsh Test and it’s definitely worth a read. I can imagine when this was performed in the courtroom it did elicit a few gasps.

A few useful links:

http://www.dplylemd.com/book-details/howdunnit-forensics.html

http://www.atlasobscura.com/articles/marsh-test-arsenic-poisoning

http://www.huffingtonpost.com/sandra-hempel-/arsenic-the-nearperfect-m_b_4398140.html

http://www.dartmouth.edu/~toxmetal/arsenic/history.html

 

Howdunnit Forensics Cover

 

How Old Is That Fingerprint?

Fingerprint

Fingerprints are useful forensic science tools. They’ve been so for over 100 years. Mainly, it’s the pattern of the ridges on the fingertips that supply the useful information. We know that everyone has different fingerprints and we know that they do not change throughout the person’s life. This means that they are highly reliable sources for identification and for discrimination between two individuals. Law enforcement has employed this for years.

But several newer techniques and analyses allow investigators to go even deeper. The skin cells, that are part of a fingerprint, can often yield DNA. Chemicals in the print residue can sometimes reveal if the person has used or handled such substances as cocaine. Other analyses are underway that might make fingerprints even more useful.

One question that frequently plagues crime scene investigators is exactly when a print was laid down. This determination can make a huge difference. Let’s say that a print is discovered at a homicide scene and the primary suspect says that he had been at that location but that that had taken place a week earlier. Not on the day of the killing. Is he telling the truth? Or simply trying to throw the police off and make an excuse for the evidence they collected against him? It would be nice to know if the print was 24 hours old or seven days old.

Research is currently underway by Shin Muramoto and his colleagues and they reported their initial findings in a recent article in Analytical Chemistry. They discovered that a chemical found in fingerprints known as palmitic acid migrates away from the ridges at a predictable and consistent rate. By looking at this migration pattern they are able to determine whether the print is fresh or up to four days old. They are looking to extend this envelope to a longer period of time. But you can see, that even this level of discrimination could help—or not—- the suspect in the above scenario.

 

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

F&F200X302.jpg

More Info and List of Included Questions

MF&F 200X320

More Info and List of Included Questions

 

Crime and Science Radio: Crime Scenes, Criminalistics, and the Cutting Edge

Crime and Science Radio: Crime Scenes, Criminalistics, and the Cutting Edge in Los Angeles: An Interview with Former LASD Criminalist Professor Donald Johnson of California State University, Los Angeles

BIO: Professor Donald James Johnson is an expert on criminalistics, with emphasis on crime scene investigation and reconstruction (homicides and sexual assaults), and forensic biology. His research interests include the application of new technologies to the field of criminalistics. He was formerly a senior criminalist at the Los Angeles County Sheriff’s Department, where he was involved in the scientific investigation of violent crimes.

NOTE: This show was recorded live at the MWA-LA Chapter meeting in Los Angels, CA

LISTEN: LISTEN: http://www.blogtalkradio.com/suspensemagazine/2016/09/10/crime-and-science-radio-with-special-guest-dr-donald-james-johnson

Link will go live Saturday 9-10-16 at 10 a.m. Pacific

LINKS:

California Forensic Science Institute: http://www.calstatela.edu/hhs/cfsi

School of Criminal Justice and Criminalistics at CSULA: http://www.calstatela.edu/hhs/crim

CSULA Masters in Criminalistics http://ecatalog.calstatela.edu/preview_program.php?catoid=11&poid=3452

Los Angeles County Sheriff’s Department Scientific Services video: https://www.youtube.com/watch?v=SboLJ7WwnXQ

Los Angeles County Sheriff’s Department: http://sheriff.lacounty.gov

American Academy of Forensic Sciences http://www.aafs.org

 
 
%d bloggers like this: