Typically, DNA profiles from a crime scene are compared with suspects or police databases. When investigations stall, the new analysis can provide completely new information.
So far, police have been able to determine eye colour, hair colour and geographic origin.
If we have a DNA trace at a crime scene, we can analyse the DNA and determine the age of the person who left the trace, with a certain margin of error, says Maja Sidstedt, senior molecular biologist at the National Forensic Centre (NFC) in Linköping, where the police's DNA analyses are done.
Used for serious crimes
The new method will primarily be used in serious crimes - such as rape and murder - where a suspected perpetrator is missing and where regular database searches have not yielded results.
Currently, the method requires relatively large amounts of DNA from a single individual, which means that it mainly works on traces of blood or semen, explains Maja Sidstedt.
She is not sure whether the method can also be used to solve cold cases, where the police have closed the investigation without having caught the perpetrator.
Unfortunately, there are still limitations to the method because it requires a lot of DNA, she says.
Analysing the gene's on/off switch
The new method involves estimating the perpetrator's age within a certain range by analysing the chemical changes (methyl groups) on the DNA molecule.
Methyl groups act as switches to turn genes on or off, and they naturally change over time. The process is called DNA methylation.
DNA methylation is widely used in clinical research related to aging and how we can slow down aging. Or understand why some people age faster than others, says Maja Sidstedt.
Future technology detects whether the perpetrator smokes
NFC is also participating in a large EU-funded research project that runs until 2029. The goal is to develop even more sensitive methods for age assessment.
In the future, we hope to become more accurate in terms of age assessment by being able to perform this type of analysis on significantly smaller amounts of DNA, for example from snus or cigarette butts, says Maja Sidstedt, who is project manager at NFC in the research project.
The research also indicates that DNA methylation may in the future reveal even more details about a perpetrator, for example whether the person is a smoker or not.
Facts: About DNA
All cells in the body have the same set of DNA. The DNA molecule contains all the genetic information in living organisms. DNA is found in all cells (except red blood cells).
In DNA there are genes, each of which is a DNA sequence that contains instructions for how cells should manufacture the proteins that the organism needs. Genes are said to "code" for a protein, which is involved in carrying out the functions of the cell.
Within a species, all individuals have the same genes. A human has approximately 20,000 genes and a potato has 40,000.
To obtain a DNA profile in a criminal investigation, DNA from, for example, a suspect is analysed and compared to the DNA in the trace. This involves examining a small part of the genetic material called STR markers, which vary between individuals. After the DNA analysis, the results for the examined STR markers are displayed as a series of numbers called a DNA profile.
DNA is an abbreviation for the English word deoxyribonucleic acid, which is translated into Swedish as deoxyribonucleic acid.
Source: Genetics Committee and Maja Sidstedt, National Forensic Center (NFC)
The police's new method for age assessment with in-depth DNA analysis is based on epigenetics, which includes DNA methylation.
Epigenetics is about how cells control which genes are on or off without changing the DNA code itself.
One of the processes the body uses to do this is called DNA methylation. This involves placing small chemical groups (methyl groups) directly on the DNA sequence to turn off a gene.
Methyl groups act as biological switches that turn genes on or off and change naturally over time.
In short, the new method involves analysing the modification (the chemical changes, the methyl group) that is on the DNA molecule. By studying the changes, it is possible to estimate the person's chronological age within a certain interval.
