You’ve seen it on TV. Crime scene investigators show up at what might be a murder scene. There are blood spatters—but no body. Who’s the victim? Now, a new technique developed in the Netherlands might help real-world investigators establish the age of the victim using only blood. The research was published in the journal Current Biology. [Dmitry Zubakov et al., "Estimating human age from T-cell DNA rearrangements"]
Usually, age is determined by physical characteristics, such as teeth or bones. Great—if you have a body. Researchers have tried unsuccessfully to use blood. But in this study, the scientists used immune cells called T-cells. T-cells recognize invaders through receptors that match molecules on bacteria, viruses, even tumors. The cellular activity that produces these receptors also produces a type of circular DNA molecule as a by-product.
The number of these receptor by-products declines regularly over time. So scientists devised a test to measure the molecules—and use that to infer someone’s age based on his or her blood. The results apear to be accurate to within plus or minus nine years. So forensic scientists could use a bloodstain to narrow a victim’s age to within two decades. That’s a big range—but it could help solve crimes when the victims can’t be found.
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