Blood spatters and saliva at crime scenes can accurately reveal the age of a missing victim or suspect using a new forensic test.
Scientists at King's College London have developed a technique which uses artificial intelligence to analyse age-related biomarkers.
The technique was able to predict the age of sample donors to within an average of four years.
Dr David Ballard said: "Our study uses a novel method to improve the accuracy of predicting age. This is the first study to test next generation sequencing and machine learning technologies together to estimate age from blood and saliva samples."
The team identified 16 key genetic biomarkers for ageing and put them to the test using data from 1,156 blood samples.
With the help of AI "machine learning" software, the researchers found that blood provided a good way to guess a person's age. Other tests revealed similar results from saliva.
The findings appear in the journal Forensic Science International.
Senior author Dr Denise Syndercombe-Court, also from King's College London, said: "Through further research, these findings could provide a basis for combined analysis techniques that would be of substantial value in forensic investigations in the future."