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Category Archives: High Tech Forensics

Your Hair and Your ID

 

We’ve known for years that DNA can be obtained from hair and this can be used for identification. If part of the follicle, or bulb, is present, then nuclear DNA can be retrieved and a complete DNA profile can be created. If only the hair shaft is available, then mitochondrial DNA is available and this can help narrow the identity of an individual by showing that the person belongs to a specific maternal line. Not nearly as good as nuclear DNA but this does focus the suspect field to a single maternal line.

But what if the hair shaft could be even more discriminatory? What if it could ID a specific individual and not just someone in the maternal line? Most hair found at crime scenes has been shed naturally and therefore has no follicular material, which might be present if the hair had been yanked free. This means that typically only mitochondrial DNA is available to the crime lab. 

But new studies have found an ultra-sensitive method for determining proteins within the hair shaft itself and it turns out that the types and amounts of the proteins present might be highly specific from individual to individual. This technique obviously is not ready for prime time yet, but it’s something to keep an eye on.

Science Article: https://www.sciencemag.org/news/2019/11/scientists-can-now-identify-someone-single-strand-hair

 

DNA Comparisons in 12 Seconds?

 

Though there are DNA techniques such as Familial and Phenotypical analyses that can narrow the search for a suspect, in the end, DNA is most useful if it can be profiled and matched against another sample. Databases play a large role in such comparisons when an unknown crime scene sample is obtained. Even if no suspect is on the radar, a “hit” on a database comparison can lead investigators down the right path. But these take time. And if a killer is “out there,” time is often critical. What if investigators could obtain a sample at the scene and compare it against 20 million databases sample in only a few seconds? That would be amazing. But guess what? With the FastID algorithm, it seems to be possible.

Could be a game changer for law enforcement.

PHYS.ORG Article: https://phys.org/news/2019-06-record-breaking-dna-comparisons-fast-forensics.html

 

Criminal Mischief: The Art and Science of Crime Fiction: Episode #17: DNA and Twins

DNA Replication

 

LISTEN: https://soundcloud.com/authorsontheair/criminal-mischief-episode-17-dna-and-identical-twins

PAST SHOWS: http://www.dplylemd.com/criminal-mischief.html

SHOW NOTES:

For years it was felt that the DNA of identical twins was indeed identical. Since they come from a single fertilized egg, this would seem intuitive. But, nature likes to throw curve balls—and the occasional slider. After that first division of the fertilized, and after the two daughter cells go their way toward producing identical humans, things change. And therein lies the genetic differences between two “identical” twins.

LINKS:

One Twin Committed the Crime—but Which One?: https://www.nytimes.com/2019/03/01/science/twins-dna-crime-paternity.html

The Claim: Identical Twins Have Identical DNA: https://www.nytimes.com/2008/03/11/health/11real.html

The Genetic Relationship Between Identical Twins: https://www.verywellfamily.com/identical-twins-and-dna-2447117

Identical Twins’ Genes Are Not Identical: https://www.scientificamerican.com/article/identical-twins-genes-are-not-identical/

Rare Australian Twins Are “Semi-Identical,: Sharing 89 Percent of Their DNA: https://www.inverse.com/article/53633-semi-identical-twins-share-78-percent-of-dna

 

Criminal Mischief: Episode #06: Is It Harder To Write Crime Fiction Today?

AOTA Graphic

 

Criminal Mischief: Episode #06: Is It Harder To Write Crime Fiction Today?

LISTEN: https://soundcloud.com/authorsontheair/criminal-mischief-episode-06-is-it-harder-to-write-crime-fiction-today

Is It Harder To Write Crime Fiction Today? Notes:

Do modern forensic science and police investigative techniques make creating compelling crime fiction more difficult? Are there simply too many balls to keep in the air? Too much to consider? Or is now little different from then?

The Past, the present, and the future

Forensic Science timeline—-a fairly new discipline

Basic Science, then Medicine, finally forensic science

Personal ID

Visual
Bertillon
West Case
Facial recognition
Behavioral Profiling

Prints, ABO type, DNA, DNA Phenotype

Fingerprints—-then and now

Vucetich—the Rojas case
Stella Nickell Case
Touch DNA
Touch Toxicology

Toxicology

From arsenic to GC/MS

Blood Typing

ABO can exclude but not ID

DNA

Nuclear
Mitochondrial
Familial—Grim Sleeper case
Phenotypic Analysis

Electronics

Cell phones, computers, emails, texts, VMs

LINKS: 

Forensic Science Timeline: http://www.dplylemd.com/articles/forensic-science-timeline.html

History of Fingerprints: http://onin.com/fp/fphistory.html

Brief History of Poisons and Forensic Toxicology: https://www.okorieokorocha.com/poisons-and-forensic-toxicology/

History of Forensic Ballistics: https://ifflab.org/the-history-of-forensic-ballistics-ballistic-fingerprinting/

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

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

Stella Nickell Wikipedia: https://en.wikipedia.org/wiki/Stella_Nickell

DNA Profiling: https://en.wikipedia.org/wiki/DNA_profiling

Mitochondrial DNA: http://www.dplylemd.com/articles/mitochondrial-dna.html

Familial DNA: http://www.dnaforensics.com/familialsearches.aspx

Grim Sleeper/Lonnie Franklin case: https://en.wikipedia.org/wiki/Grim_Sleeper

Is DNA Phenotyping Accurate: https://www.smithsonianmag.com/innovation/how-accurately-can-scientists-reconstruct-persons-face-from-dna-180968951/

DNA Phenotyping Examples: https://snapshot.parabon-nanolabs.com/examples

Bertillon and the West Brothers: http://www.nleomf.org/museum/news/newsletters/online-insider/november-2011/bertillon-system-criminal-identification.html

 

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.

 

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

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Firearm Examinations Go 3D

Unknown

People often use the term ballistics when they actually mean firearms examination. Ballistics, in its purest definition, is the flight pattern analysis of things like rocks, bullets, artillery shells, and rockets. But the term ballistics has become the vernacular for firearms examinations.

One of the important analyses that takes place in many homicide investigations, is a comparison of bullets removed from a corpse with those test fired by a suspect weapon. As the bullet travels down the barrel, scratches and grooves are cut into the outside of the bullet by the spiral rifling within the barrel and these apply unique characteristics to the bullet. If the test-fired bullet and the bullet removed from the victim can be matched in this fashion, it suggests that the bullet came from that gun to the exclusion of all others.

But, it’s not that simple. During the manufacturing process of the barrel, a tool is used to mold the shape the barrel’s lumen or to hollow out its interior. This process creates the bullet’s pathway from the firing chamber to the muzzle and also adds the rifling characteristics of the weapon’s barrel. Each is different since the molding or cutting process varies with each attempt.

As a tool is used to manufacture barrel after barrel, the tool itself also changes. It is worn, chipped, grooved, and damaged with each use. Think about your kitchen knives. Over time they become dull and must be resharpening. This is because the tool – – the kitchen knife – – itself is altered with each use. This means that as barrels are produced by a particular manufacturing tool, each will be slightly different. However, if two barrels are made by the same tool consecutively, the differences can be so small as to be undetectable. This could lead to false matches.

The same is true of the gun barrel as it is used. With each firing, the grooves are microscopically altered. If a bullet is obtained from the crime scene and is compared to one test fired from the actual murder weapon, it might not match if the weapon has been fired many times between the killing and its discovery. The barrel is altered each time a bullet passes through it and this can be enough to make a match impossible.

To help examiners, the National Institute of Standards and Technology (NIST) has developed a database of 3-D images which will hopefully help examiners be more accurate in their assessments. Obviously, this data will be subject to the same vagaries as described above but with these clearer, three-dimensional images some of the confusion might be reduced and matches might be more accurate down the road. This will be interesting to keep an eye on.

 

Can Your DNA Reveal Your face?

Parabon_Snapshot_Workflow_Diagram

You’ve seen it on TV. The CSI-types plug in a DNA sample and like magic a 3-D, holographic image of the bad guy pops up like a ghost. Or some such stuff. Pretty far-fetched. Or is it?

DNA analysis is primarily used for comparison, meaning that a sample obtained from a crime scene is compared with a sample obtained from a suspect to see if the DNA from the scene belongs to the suspect, or not. This is how many cases are solved. DNA is highly accurate for making such comparisons.

But what if there is no suspect and therefore no DNA to compare with that obtained at the crime scene? The police will then go to databases such as CODIS to see if the perpetrator has DNA on file from previous crimes. Often this helps. Often a match is made this way. But what if the perpetrator is not in the system? The police are back to square one.

DNA can of course reveal the sex of the individual very easily. It can also often determine hair and eye color and other physical features. But can it give a “picture” of the individual who left the DNA behind? Not yet, but things are moving that way.

Here are a few fun articles on this technique:

DNA Phenotyping Recreates the Face of an Alleged Serial Killer: https://www.forensicmag.com/article/2016/08/dna-phenotyping-recreates-face-alleged-serial-killer

First DNA-Phenotyped Image of “Person of Interest” in Double Homicide: https://www.forensicmag.com/article/2015/01/first-dna-phenotyped-image-person-interest-double-homicide

Phenotyping and Cold Cases:
https://www.defrostingcoldcases.com/phenotyping-cold-cases/

 

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

 

Luminol and A Malarial Drug Team Up to Find Hidden Blood

luminolpowderamazon_01

 

Sometimes blood shed at a crime scene is easily visible but at other times less so. Maybe it’s a very small amount, or perhaps soaked into a patterned carpet, or secreted in the gaps between tiles and baseboards. Perhaps the killer has cleaned up the crime scene, thinking that if the blood is not visible, it’s not findable. Maybe he even washed the blood off is hands and watched it circle down the drain. Gone forever.

Or maybe not. Things such as luminol can uncover these hidden stains.

Luminol is actually quite sensitive for finding blood. Spraying it on a wall that has been wiped clean of visible blood, or often even if painted over, and then turning out the lights will reveal the glowing pattern of the blood splatter. This helps not only to locate the blood but also to identify patterns, which, in turn, might help re-create the crime scene. Such reconstructions are critical in bloody homicide investigations.

From FORENSICS FOR DUMMIES:

Reconstructing the crime scene from bloodstains 

Contaminated evidence is no evidence at all, so investigators have to document bloodstain and spatter patterns in a timely and logical fashion. Police, fire, and rescue personnel can alter or contaminate the blood evidence, as can any unnecessary foot traffic at the crime scene. For that reason, investigators need to take control of the scene immediately and consistently. 

Unless they’re high‐traffic public places, indoor scenes usually can be preserved long enough for investigators to obtain needed information. Outdoor scenes, however, are subject to environmental influences, and public places require investigators to gather information more urgently. 

Investigators carefully photograph bloodstains. Initial photographs capture an overall view of the scene. Subsequent pictures gradually move in on individual stains. The photographer takes pictures of individual stains close enough to reveal all needed detail, and should include a ruler or other measuring device to provide a scale reference. In homicide cases, investigators check out the body and any associated bloodstains or spatter first. After the body is removed, investigators turn their attention to other spatters. 

Some bloodstains are latent (invisible to the naked eye). Investigators often use luminol to expose these hidden stains. Luminol is a chemical that reacts with the hemoglobin in blood to produce a complex substance that luminesces (glows). Luminol is extremely sensitive, detecting blood in concentrations as low as one part per million. Investigators darken the room and spray luminol over areas where they suspect blood to be. When blood is present, stains glow a bluish‐white, and the photographer takes pictures of the glowing pattern. 

Luminol also can reveal bloody tracks that indicate the perpetrator’s movements or escape route and drag marks that show whether anyone moved the body. Luminol is so sensitive that it can uncover blood in cracks, crevices, and even areas where someone has tried to clean it. 

It’s important to note that many substances can interfere with or confuse luminol pattern analysis. Bleach and other cleaning agents, certain paints and varnishes, and even some fruit juices are examples. 

After photographers take an adequate number and variety of photographs, crime‐scene analysts complete their analyses and create a report that may include implications of the victim’s and assailant’s locations at each stage of the crime, the number and types of injuries inflicted, and the exact sequence of events (see the next section to understand how analysts gather this information).

But, as mentioned above, there are things that interfere with this chemical process. Certain fruit juices, bleaches, horseradish and turnips, and other chemicals will also react with luminol and this can confuse the issue.

A recent study reported in Science Daily suggests that a new method might help solve some of these problems. Combining luminol with the antimalarial drug Artemisinin seems to reduce this cross-reactivity and therefore more specifically display the true blood spatter pattern. Obviously, more research is needed, but this is a potentially useful tool.

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