New forensic technique may better gauge age at death | Science News for Students

New forensic technique may better gauge age at death

Used with skulls, the estimates should fall within three years of an adult’s actual age
May 21, 2019 — 1:05 pm EST
a photo of Andrey Gizdov holding a skull at Intel ISEF 2019

Andrey Gizdov, 18, came up with a new and potentially better way to estimate the age at death for human remains. It’s based on a CT scan of the person's skull.

Kyle Ryan/SSP

PHOENIX, Ariz. — When detectives analyze human remains, they often have many questions. One of the most common: How old was the person at death? A teen in Ackworth, England has developed a new way to figure that out. And it may be more accurate than techniques typically used today.

Estimating the age of unidentified human remains is difficult, notes Andrey Gizdov, an 18-year-old who attends the Ackworth School. Because the skull usually remains intact, forensic experts currently use several techniques that focus on these bones to gauge skeletal age. The techniques often focus on cranial sutures (KRAY-nee-ul SOO-churz). These are seams where individual bones in the skull meet and merge. As people age, these seams continue to fuse ever more strongly — even in mature adults. That underlies Andrey’s new technique.

The teen showcased his research here, last week, at the Intel International Science and Engineering Fair. This competition was created by Society for Science & the Public in 1950. Its 2019 event brought together more than 1,800 finalists from 80 countries. (The Society also publishes Science News for Students.)

Andrey’s technique homes in on details present in X-ray images that are created by computerized tomography, also known as CT. This technology scans an object or body part. The resulting X-ray images look like hundreds of sequential slices through the object. A computer merges those images into a file to create a digital 3-D model of the scanned object. A computer can then display any cross-section of the object and from any angle.

For his project, Andrey reviewed skull CT scans that had been performed by others. He focused on a structure known as the sagittal suture. Along the centerline of the skull, it runs from the top of the forehead back to the crown of their head. Up close, that seam resembles a meandering river.

a 3-D model of a human skull, with the seam between bones on the top of the skull highlighted in red
The new aging technique focuses on the seam between bones along the top of the skull (depicted in red).
BodyParts3D/Anatomography/Wikipedia Commons (CC-BY-SA-2.1-JP)

The CT’s X-rayed slices of this suture were about a millimeter (1/25th of an inch) thick, Andrey says. For an adult skull, there would be some 350 or so sequential images available to analyze. In most of these, the suture showed up as a V-shaped notch between the bones, explains Andrey. Think of the bottom of the V as a valley. As a person ages, that valley gradually fills in with calcium-based minerals. Usually, it fills in from valley floor up toward the top.

Andrey used computer software to analyze each image. The software measured how deeply the V-shaped notch had filled in with minerals. He also used the software to estimate the density of those minerals. (The darker the notch shows up in the scans, the less dense the bone is, Andrey notes.) Then, the teen took all of his measurements and calculated an average for both the depth and the density of minerals along the entire suture.

He did this for the sagittal suture in 42 skulls. Each came from known persons. Their ages at death — from 19 to about 60 — also were known. By comparing the sutures, he showed that this feature changes with age. Andrey then used those 42 data points to develop a mathematical equation. It related age at death to the depth and density of calcium minerals in the sagittal suture.

The teen then used his equation to predict the age at death from skulls of other people. Their ages at death, too, were known. He typically was able to estimate a person’s age at death to within 3.2 years. That’s a big improvement over current methods. Currently, he notes, researchers usually can estimate age at death only to within 10 years.

One day, Andrey’s technique might help archaeologists analyzing ancient remains. Still, the technique isn’t perfect. After all, everyone ages differently. Plus, other factors might affect how quickly and how well someone’s sagittal suture fills in with minerals. For instance, suffering from malnutrition might alter suture filling, says Andrey. So might certain diseases, such as osteoporosis (Os-tee-oh-por-OH-sis), which weakens bones.

Power Words

(more about Power Words)

average     (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.

calcium     A chemical element which is common in minerals of the Earth’s crust and in sea salt. It is also found in bone mineral and teeth, and can play a role in the movement of certain substances into and out of cells.

computerized tomography     (CT, for short). A special kind of X-ray scanning technology that produces cross-sectional views of the inside of a bone or tissues of the body.

cross section     A term for the view of some three-dimensional solid as it would appear if a knife had cut through the structure, separated it in two, and then one of those pieces was now looked at edge-on from one of the cut sides.

crown     The upper region of something.

density     The measure of how condensed some object is, found by dividing its mass by its volume.

digital     (in computer science and engineering)  An adjective indicating that something has been developed numerically on a computer or on some other electronic device, based on a binary system (where all numbers are displayed using a series of only zeros and ones).

equation     In mathematics, the statement that two quantities are equal. In geometry, equations are often used to determine the shape of a curve or surface.

factor     Something that plays a role in a particular condition or event; a contributor.

forensic     And adjective referring to the use of science and technology to investigate and solve crimes.

fuse     To merge two things together, often along some seam.

Intel International Science and Engineering Fair (Intel ISEF)      Initially launched in 1950, this competition is one of three created (and still run) by the Society for Science & the Public. Each year now, approximately 1,800 high school students from more than 80 countries, regions, and territories are awarded the opportunity to showcase their independent research at Intel ISEF and compete for an average of almost $5 million in prizes. 

mature     (adj.) Connoting an adult individual or full-grown and fully developed (non-juvenile) form of something. (verb) To develop toward — or into — a more complex and  full-grown form of some individual, be it a plant, animal or microbe.

mineral     Crystal-forming substances that make up rock, such as quartz, apatite or various carbonates. Most rocks contain several different minerals mish-mashed together. A mineral usually is solid and stable at room temperatures and has a specific formula, or recipe (with atoms occurring in certain proportions) and a specific crystalline structure (meaning that its atoms are organized in regular three-dimensional patterns). (in physiology) The same chemicals that are needed by the body to make and feed tissues to maintain health.

osteoporosis     A disease in which bones become weak, brittle and at risk of breaking.

seam     The site where two or more fabrics are held together with stitches or are fused together by heat or glue. For non-fabrics, such as metals, the seams may be crimped together or folded over several times and then locked in place. (in geology) A layer of rock, underground, where some mineral, such as coal or iron ore, has developed.

skull     The skeleton of a person’s or animal’s head.

software     The mathematical instructions that direct a computer’s hardware, including its processor, to perform certain operations.

suture     (in anatomy) The joint between two bones that eventually fuses into an immobile seam.

technology     The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.

X-ray     A type of radiation analogous to gamma rays, but having somewhat lower energy.