14 in carbon 14 dating
The researchers found that certain soft tissues — notably blood, nails and hair — had radiocarbon levels identical to the contemporary atmosphere.
Therefore, the radiocarbon level in those tissues post-mortem would indicate the year of death.
Barring any future nuclear detonations, this method should continue to be useful for year-of-birth determinations for people born during the next 10 or 20 years.
Everyone born after that would be expected to have the same level of carbon-14 that prevailed before the nuclear testing era.
The researchers found that if they assumed tooth enamel radiocarbon content to be determined by the atmospheric level at the time the tooth was formed, then they could deduce the year of birth.
They found that for teeth formed after 1965, enamel radiocarbon content predicted year of birth within 1.5 years.
The researchers wanted to find out if they could identify a person's year of birth or year of death using precise measurements of carbon-14 levels in different post-mortem tissues.
They measured carbon-14 levels in various tissues from 36 humans whose birth and death dates were known.
Danielle Mc Leod-Henning is a program manager and physical scientist at NIJ.
The new method is based on the fact that over the past 60 years, environmental levels of radiocarbon have been significantly perturbed by mid-20th-century episodes of above-ground nuclear weapons testing.