Uncovering the age and origin of a vandalized statue of Christ in Chile could come down to atoms. Chile’s Crime Investigation Police (PDI), trained and equipped with the help of the IAEA, are using nuclear techniques to study the remnants of the figure damaged during a student protest in June 2016 in the capital Santiago de Chile.
“This case of vandalism has caused turmoil countrywide,” said Francisco Torres Roquer, Head of the Microanalysis Department of Chile’s PDI. The analyses aim to confirm the age and origin of the figure, he said. Determining the historical value of the statue is an important element in the ongoing investigation.
Pursuing criminals with nuclear technology
With advances in technology, criminals have developed more sophisticated methods that make it harder for prosecutors to track evidence. Nowadays, the evidence they leave is so scarce and microscopic that investigators refer to it as ‘trace evidence’.
Nuclear techniques like X ray spectroscopy, X ray diffraction or neutron activation analysis (see The Science box) offer investigators the possibility to analyse this trace evidence with precision. Not only can these techniques be applied to very small samples, but in most of the cases they do not destroy the evidence, which is why specialists often use them to check works of art, historical artifacts and crime-related forensic samples.
Not destroying the evidence is a key requirement. Regulations demand that both the prosecutor and the defendant should have access to it. “But any study of evidence using conventional methods involves altering the sample’s chemical elements or even destroying the sample, which does not allow the other party to analyse it and results in legal disadvantages,” Torres Roquer said. “It’s a big problem for us.”
To overcome this, PDI requested support from the IAEA to increase the accuracy of its evidence analysis, complementing their conventional methods with nuclear technology. The IAEA worked with PDI and the Chilean Nuclear Energy Commission, providing spectroscopy machines and training in X ray fluorescence, X ray diffraction and neutron activation analysis. These techniques were used to identify the pigments used in the production of the figure of Christ.
PDI is also using these techniques in other criminal investigations related to pieces of art, including stealing and falsification. They also use them to study the composition of gunshot residue particles —usually taken from suspects— or to establish the composition of materials adhered to bullets to trace their trajectory. Similarly, police can use these techniques to identify minerals in samples of soil and sediment residues and compare them to minerals taken from the soil and sediments of the suspected crime scene.
IAEA technical cooperation projects have supported the establishment of a national network of forensics experts using non-destructive nuclear techniques to characterize, identify and analyse forensics samples. This national network is coordinated by PDI and includes the Chilean Nuclear Energy Commission, the University of Chile and the University of Concepción.