Posts Tagged ‘forensics’
Sherlock the German Corpse-Sniffing Vulture Isn’t Quite As Helpful As Hoped
In Sherlock’s case, he would rather walk than fly. When he does find something, it’s usually an animal rather than the stinking human burial shroud that he is supposed to be looking for. And the bird is, understandably, a bit shy around all the human attention, much unlike the famous fictional detective for whom he's named (Holmes, if I remember correctly, was always either sprinting or in a drug-induced near-comatose state, and was not known for being shy).
"The bird is naturally anxious, and he would hide in the woods or bolt," his trainer tells the BBC. These aren’t the traits the Germans were looking for in their new gumshoe. Without the elder Sherlock to lead the way, the trainers feel little hope that the younger vultures, Columbo and Miss Marple, will fare any better.
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Sherlock the German Corpse-Sniffing Vulture Isn’t Quite As Helpful As Hoped
In Sherlock’s case, he would rather walk than fly. When he does find something, it’s usually an animal rather than the stinking human burial shroud that he is supposed to be looking for. And the bird is, understandably, a bit shy around all the human attention, much unlike the famous fictional detective for whom he's named (Holmes, if I remember correctly, was always either sprinting or in a drug-induced near-comatose state, and was not known for being shy).
"The bird is naturally anxious, and he would hide in the woods or bolt," his trainer tells the BBC. These aren’t the traits the Germans were looking for in their new gumshoe. Without the elder Sherlock to lead the way, the trainers feel little hope that the younger vultures, Columbo and Miss Marple, will fare any better.
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Saliva Science: New Forensics Tool Can Determine a Person’s Age from a Spit Sample
The method relies on a process called methylation, which is a chemical change to one of the four building blocks of a person’s DNA. Methylation changes as our bodies grow older, contributing to age related diseases. In extracting DNA from saliva samples from more than 100 test subjects, the team found that it could zero in on a person’s age within five years by looking at just two of the 3 billion blocks that make up the human genome--such is the strong correlation between methylation and age.
But the approach could go beyond simply being a forensic tool employed at crime scenes. DNA age (or “bio-age”) doesn’t always line up perfectly with chronological age. So methylation doesn’t always give a precise chronological accounting of years gone by (hence the five year margin of error--still very precise by existing standards). But it does tell you how old you are in DNA years, so to speak.
So physicians could use the unobtrusive saliva analysis to determine patients’ bio-ages, tailoring medical tests and interventions to a person’s bio-age rather than his or her chronological age. That means fewer unnecessary tests and a better, more effective application of medical science to prevent age-related illnesses.
New Method Punches Holes in Hair to Create a Forensic Record Of What You Ingested, Hour By Hour
There are existing methods of testing hair samples for carbon clues, but they tend to destroy small samples within the hair and they certainly don’t give time-based measurements. That is, they can distinguish what’s in your diet, but have trouble creating a chronology of when you ate what, much less an accurate hour-by-hour record.
The new method, developed at Pacific Northwest National Laboratory, uses an ultraviolet laser that is careful to break up materials in the hair rather than scorch them as other lasers typically do. Once broken apart, the particles can be fed into a mass spectrometer for analysis.
From that analysis of carbon isotopes, researchers can reconstruct a forensic record of the person to whom the sample belonged. Specifically, they can see what and when you’ve been eating (and from that perhaps deduce where you’ve been eating as well).
But while carbon betrays what a person has been eating, other elements could paint an even more detailed portrait of his or her life. Oxygen isotopes are tied to the water cycle and sulfur to bedrock, while nitrogen could help further specify exactly what a person has been consuming. As such, the PNNL team is now adapting their laser technique to analyze those isotopes as well.
See some small-scale laser ablation below.
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Blood Simple: Improving Crime-Scene Analysis Techniques
Where
Investigators use spray-on reagents to locate blood spatter that’s too small to see. But chemicals can contaminate evidence or give false positives. Stephen Morgan and Michael Myrick of the University of South Carolina have developed an infrared camera system that exposes microscopic traces of blood without using chemicals. The device targets blood proteins, which remain long after visible blood has been wiped away, filtering background infrared to reveal blood residue that can’t be seen with the naked eye.
How
Detectives use spatter reconstructions to piece together what a crime might have looked like as it happened. Typically, investigators pin string from blood stains to a possible point of origin, but this method overlooks the fact that blood drops arc through the air. Forensic-surveying engineer Ursula Buck and her team at the University of Bern in Switzerland use laser scanners and imaging software to re-create accurate spatter trajectories. First, digital photographs of the crime scene are stitched into a panorama that shows blood-stain size and location, while the laser scanner creates a 3-D rendering of the room. The mass of each droplet is then calculated based on the size of the stain. Finally, using an algorithm developed by the Swiss team, every drop of blood has its path re-created, no string attached.
Who
Forensic scientists had no reliable method for establishing age using blood samples before last November, when Manfred Kayser and his colleagues at Erasmus MC University Medical Center Rotterdam in the Netherlands announced that they had developed a process to determine age, plus or minus nine years. The test examines white blood cells called T cells by looking for the snippets of DNA that form inside newly made T cells as they fight infections. As we age, our bodies create fewer T cells (a reason the elderly are more susceptible to colds). The more of these DNA snippets, the younger the perp. “Police are desperate to get information,” Kayser says. “We’re mining human biology to give them a new tool.”
Archive Gallery: Science Solves Crimes
How earographs, invisible ink detectors, and the famed "Stamp Detective" used science to catch unsuspecting crooks.
Nowadays, we're so used to seeing forensics dramatized on TV that we take criminology for granted, but for a generation raised on Edgar Allan Poe, Sir Arthur Conan Doyle and Agatha Christie, these developments were nothing short of marvelous.
Like the first article in our series says, science has trumped Sherlock Holmes as the most trustworthy detective. It takes a clever man to detect circumstantial evidence, but a few damning clues can't compare to solid proof that a week-old bloodstain comes from a particular person. To help our readers understand how the scientists glean knowledge from trace evidence, we visited experts like firearms identification pioneer Calvin Goddard, who used his helixometer, to show us how uses microscopic grooves to differentiate between bullets.
Sometimes we covered cases that were less violent. In a feature called "Hidden Crime Clues Bared by Chemist's Magic," we described how scientists could decode messages written in invisible ink by dipping them in various fluids. A couple of years later, police squads nationwide intercepted similar messages by using amphibian airplanes to trail carrier pigeons owned by the underworld. If that sounds a little quaint, you'll laugh at gems like our feature that lauded earography, the science of identifying criminals by their ears.
As silly as it sounds, the earograph apparatus isn't the strangest tool detectives-turned-scientists used during the early days of modern forensics. Click through our to see what else we have in store.
New Forensic Method Can Determine a Person’s Age from Blood Left at a Crime Scene
The test isn’t perfect; that is, it has a margin of error of nine years in either direction. But in cases where police are trying to build a profile of an unknown person, the test can narrow the possibilities down to a generational cohort spanning about two decades. Previous attempts to do so have proved inaccurate, but this attempt at deriving a phenotypic human trait from DNA information is at least as accurate, if not more so, than other profiling methods like a similar means of determining eye color from DNA.
The science turns on a certain molecular process tied to the T cells in blood. The ability of T cells to recognize foreign threats depends upon the diversity of receptors that match up with characteristics found in the invaders. That diversity is achieved by a rearrangement of the T cells’ DNA over time, a process that produces distinguishable circular DNA molecules as a byproduct. Those molecules decline constantly in number over time in correlation with the person’s age.
By counting up the number of these circular DNA molecules in a sample and comparing it to the quantity of another reference gene that remains constant throughout a person’s lifetime (as a reference that compensates for the varying amount of DNA in a given sample), forensics experts can deduce, with reasonable accuracy, the age of the blood’s owner.
The method won’t be used like DNA matching that links a suspect definitively to the scene of a crime, but in situations where authorities have no leads regarding the identity of a wanted or missing person, it should help police build a more accurate profile of who it is they are looking for.