通过血液可测出受害人年龄

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 9 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.

—Cynthia Graber