What did one carbon-14 isotope say to the other carbon-14 isotope? Keep reading to find out!
What is a forensic chemist’s ideal date? A carbon date. Sounds familiar? It is popularly known to be used by scientists to learn about ancient artifacts and remains. In the past, that was the primary objective of carbon dating but recently with technological advances, it is also being utilized in knowing the ages of human remains. The method narrows down the missing person’s list in criminal cases and is even used in identifying forgeries in ancient artifacts.
Therefore, how does carbon-14 dating in forensics work? Carbon 14 atoms are created by cosmic radiation. These carbon 14 atoms react with oxygen to form carbon dioxide which gets into plant fibres through photosynthesis and essentially into every living thing, including humans.
Over the past 60 years, environmental levels of carbon have been disturbed. Since the 1950s, the radiocarbon levels have increased by 100 per cent due to the high levels of nuclear testing between the 1950s-1960s. From 1963, after a nuclear testing banning treaty, there was a drop in radiocarbon levels as radiocarbon was absorbed into oceans and the biosphere.
This accurately describes the year of death of the corpses. These fluctuations in natural radiocarbon levels mean humans living across different regions have similar and unnaturally high levels.
Forensic chemists examine the soft tissues (such as blood, tissues [JAD4] and nails) in the human remains, these are constantly remade until the human’s death and hence their carbon-14 level mimics the same level as the year the human died. Meanwhile, the year of birth is determined by the tooth enamel. Adult tooth enamel is formed at known intervals. When the tooth enamel radiocarbon level is assumed to be at the time it was formed, the year of birth can be deduced.
This method which uses Accelerated Mass Spectrometers is proven to be accurate to 1.5 years in providing the year of birth and death. New portable devices that can provide results in 2 hours (compared to the several days AMS machines take) are also being developed.
Furthermore, this method has been taken into practice in the latest cases of forensic chemistry. A case study by Cambridge used carbon dating for Disaster Victim Identification to fully confirm the year of death of victims of the Korean War.
Another case where this method is used is to identify forged paintings in forensic cases. Here instead of just carbon-14 levels, the ratio of carbon-12 (which stays the same after death) to carbon-14 (which is the same amount as carbon-12 but decays by half its amount every 5730 years) isotopes is measured. The isotope ratio of carbon-12 to carbon-14, which are in the oil paint, is found using an AMS. For example, it was used to detect a forgery in the famous Peggy Guggenheim collection.
Graph showing the decay of carbon-14 isotope. Its ratio is measured in forged painting.
Back to the question asked in the start of the article, it said to the other carbon-14 isotope “Where half you been all my life?”
- Anwesha Mazumdar
Bibliography
Bulman, Philip. “Applying Carbon-14 Dating to Recent Human Remains.” Carbon-14 dating to recent human remains, Mar. 2012, https://www.crime-scene-investigator.net/carbon-14datingtorecenthumanremains.pdf.
Brock, Fiona, and G. T. Cook. “Forensic Radiocarbon Dating of Human Remains: The Past, the Present, and the Future.” CERES Home, Equinox Publishing, 1 July 2017, https://dspace.lib.cranfield.ac.uk/handle/1826/12344.
Johnstone-Bellford, Eden, et al. “Bombs, Bodies, and Carbon-Dating Human Remains.” – Monash Lens, 11 Feb. 2022, https://lens.monash.edu/@medicine-health/2022/02/11/1384443/bomb-testing-fallout-a-forensic-boon-for-carbon-dating-time-of-death?amp=1.
Gröflin, Simon. “Radiocarbon Dating for Counterfeit Detection.” Security Forum, 20 July 2022, https://www.sicherheitsforum.ch/en/radiocarbon-datierung-zum-nachweis-von-faelschungen/.
Parker, Ann. “Biological Mysteries Decoded with Radiocarbon Dating.” Biological Mysteries Decoded with Radiocarbon Dating, Dec. 2013, https://str.llnl.gov/december-2013/buchholz.
Comments