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Category Archives: Crime Scene

Can Your DNA Reveal Your face?

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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/

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Is Fingerprint Analysis Becoming More Automated?

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Each person possesses their own unique fingerprint pattern. No two prints have ever been found to be the same. This includes identical twins, who have the same DNA profile but different fingerprints. Not sure why this is, but it is. This means fingerprints are the perfect tool for identification and comparison.

But fingerprint analysis has a problem. It is subjective, in that it depends on the skill and dedication of the examiner. Another important factor is the quality of the print obtained from a crime scene. Those done in the police station, where the suspect’s prints are rolled in ink or obtained by a digital scanner, are clean and clear for the most part. Each of the ridges is easily visible and all of the nuances of prints are readily apparent. But at the crime scene, criminals refuse to cooperate in that way. They leave behind partial, smeared, and unclear prints that make analysis difficult. They also leave prints on surfaces that aren’t the best for retaining latent prints.

This makes the examination process tedious, time-consuming, and difficult. But what if computer techniques could enhance an unclear or partial print to the point that it could be compared by the computer itself? This would narrow the choices and lighten the burden on examiners so they would have more time to focus on the details and make sure the print indeed matched or didn’t.

A new technique for automating fingerprint analysis is under development. It’s pretty cool and promises to be helpful.

 

Bugging Your DNA

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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

 

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.

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EDMOND LOCARD

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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.

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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.

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DNA Solves the 80-Year-Old Death of Belgium’s King Albert I

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Belgium’s King Albert I was found dead on February 17, 1934. The experienced rock climber was found at the base of a large formation with a gash to his head. Speculation that he was murdered ran rampant. During World War I, he had resisted Germany and attempted to block German troops from entering his country. They eventually did, but he fought them every step of the way. Was Germany somehow complicit in his untimely death?

Many felt that he had been killed elsewhere and his body dumped where it was found. The evidence suggested otherwise. His glasses were found nearly 40 feet above him – – he was very far-sighted – – and his climbing rope was still attached to his body. But, the most important evidence that suggested a fall rather than a murder was blood on the leaves near the King. If this blood was indeed Albert’s, then he must have shed it at that location, meaning he was at least briefly alive when he reached the ground at the base of the rock formation. If he had been killed elsewhere and dumped, there would have been no blood around the body. Dead folks don’t bleed. The leaves were apparently collected and preserved.

Flash forward to 2014. The blood of the leaves was tested. Not only was it human blood and but also it was matched against two relatives of the King. These results suggested that the blood was indeed the King’s blood and it had likely been shed from a head injury he received from his fall. This 80-year-old “murder” case seems to be a tragic accident.

 

Luminol and A Malarial Drug Team Up to Find Hidden Blood

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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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Webinar: What Were They Thinking? The Planning of the Perfect Murder

Join me for a fun Webinar hosted by Sister in Crime-Atlanta on Tuesday, June 13, 2017 from 7:00 to 8:30 p.m. Eastern Time. You must be a member of that chapter to join is but if you’re already a SinC National member it’s only $20.

Here is the info on the event:

When your character plans and executes “The Perfect Murder,” he always, ALWAYS makes a mistake or two. These errors ultimately lead your sleuth to the solution. In this session, Dr. D.P. Lyle deconstructs the planning, execution, and post-crime behavior of two headline-grabbing murderers–O.J. Simpson and Scott Peterson—to help mystery writers and fans better understand fictional killers from social, psychological, forensics, investigative, and motivational points of view. Q & A follows a 1-hour presentation. Forensic questions welcome!

Webinar: https://www.meetup.com/Sisters-in-Crime-Atlanta-Chapter/events/239240813/

SinC-Atlanta: https://www.sincatlanta.com

 

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