The new test is a breakthrough, particularly for victims that only report the crime after a few days. The technique is an international first and is, as of now, available to sexual assault support centres both at home and abroad.
When a victim of sexual violence reports the crime, the samples taken often contain a mixture of cells from both the victim and the perpetrator. The current standard techniques separate the sperm cells from the vaginal cells of the victim, to create a DNA profile of the perpetrator. But something it is like looking for a needle in a haystack: if there are too few cells of the perpetrator, creating a DNA profile is no longer possible. The chances of finding a useful lead are slim, particularly in cases where victims do not report the crime until several days later.
5 to 7 times more sensitive
Leuven researchers came up with a solution by combining two existing methods. With SpermFACS, researchers use fluorescence-activated cell sorting (FACS), a technology capable of recognising and selecting individual cells. A special fluid causes only the perpetrator’s cells to glow. They then pass the sample through a FACS device, a highly accurate sorting machine developed by KU Leuven. The machine recognises the luminescent cells and extracts them one by one, thereby completely separating the perpetrator’s DNA from that of the victim.
The recently published validation study shows that SpermFACS is five to seven times more sensitive than current standard methods. The test works even when there are as many as 7,500 cells from the victim for every single cell from the perpetrator. Whereas traditional techniques often fail to yield usable male DNA after 48 hours, the new technology manages to obtain DNA profiles up to at least five days after sexual contact, which significantly increases the likelihood of a match with the perpetrator.
Our new test could make a real difference to victims
prof. dr. Bram Bekaert
Prof. dr. Bram Bekaert, forensic genetics specialist at UZ Leuven: “The new SpermFACS DNA test increases the likelihood that we can still obtain reliable DNA evidence, even if the report is made late. In practice, many victims do not report the incident to the police or medical services immediately. They are in shock, feel shame or fear, or face practical barriers. If the forensic examination then takes place days later, the biological evidence often contains insufficient information. Our new test can make a real difference for victims, both in terms of legal proceedings and in terms of their sense of recognition and justice.”
Complex sexual offence records
The new method offers benefits not only in cases of late reporting. It also opens up new possibilities in complex cases, such as those involving very few sperm cells or situations where there are multiple potential perpetrators in a gang rape. By isolating sperm cells with a high degree of purity, SpermFACS not only increases the likelihood of identification but also enhances the reliability of the forensic analysis.
The method has been fully validated in accordance with international quality standards. SpermFACS is not patented, meaning that other centres and laboratories worldwide can also make use of it. The researchers hope that the technology will thus become widely adopted in forensic laboratories in the future and have a lasting impact on the approach to sexual violence. The validation of the test was published in the Analytical Chemistry journal.
Follow-up project
Professor Bekaert's team is already working on a follow-up project. Together with the biosensor group at KU Leuven, led by professor Jeroen Lammertyn, they aim to miniaturise the technology so that samples can also be analysed on a microchip. This will enable analyses to be carried out more quickly. In the future, the researchers hope to use the method to analyse contact traces on other types of evidence, such as DNA traces on clothing or objects.