Forensics: Advances in scene of crime DNA evidence

New advances in single cell DNA profiling could make it possible to identify individuals from even the smallest traces.

And a new project, led by the Earlham Institute with Liverpool John Moores University, is set to explore whether the justice system could use these to create DNA profiles from complex crime scene evidence.

A consortium has been awarded nearly £625k to explore whether cutting-edge sequencing technologies could be used by forensic scientists to identify individuals who have been involved in crimes. 

The project - Single-cell and single molecule analysis for DNA identification (SCAnDi) - involves the James Hutton Institute, University of Edinburgh, University of Portsmouth, University of Derby and Edge Hill University.

Humans shed cells wherever they go and they often tell a story. For example, depending on whether an individual is bleeding on, or touching a surface they will leave behind two different types of cell. Each of these cells can contain DNA. This is already used as evidence to identify an individual - or rule them out - in criminal cases.

However, identification becomes much more difficult when cells from multiple individuals are mixed together. Around 45 per cent of forensic samples within the UK criminal justice system are believed to contain human DNA from two or more individuals. 

If there is DNA from more than one person present, traditional analytical techniques may miss smaller traces from certain individuals, while mixed samples can also considerably reduce the success of searches against DNA databases. 

In short, it becomes more difficult to piece together a clear story of how an event took place, or to ensure justice is delivered for people involved in a crime.

Single-cell analysis allows genomes to be constructed from much smaller amounts of genetic material. It is often used to explore differences between individual cells in mixed samples. For example, it has been used in cancer research to identify different genetic mutations between cells in different parts of the same tumour.

These approaches could allow DNA profiles to be constructed from cells found at the scene of a crime. These profiles can also be linked with images of the cell, which could provide valuable contextual information to forensic experts - particularly where there are mixed samples.

Dr Nick Dawnay, Senior Lecturer at LJMU's Forensic Research Institute, said: “This project represents an exciting step forward in forensic science. Traditionally we have to work with multiple cells to generate a DNA profile and when evidence samples are mixed getting a clean single-source DNA profile is incredibly difficult. 

“The ability to not only identify an individual from a single cell but to first detect and capture that cell would represent a breakthrough.”

Dr Iain Macaulay, from the Earlham Institute, said: “Knowing the genetic origin of individual cells in a mixture - and perhaps linking that with images of the cells - could give us new information about how, when, and why this DNA ended up at a crime scene.”

He explained the project will explore not only whether single-cell approaches would be valuable in forensics, but also whether they would be practical. Engagement with the whole criminal justice system will be critical in deciding if - and how - the technology could be applied. 

“We’ll be working with people in different parts of the justice system to explore the practicalities of using this technique, and whether these approaches would fit into the way they work.” 

A key aspect of the project will be establishing a network of forensic practitioners, commercial suppliers, researchers, and investigative and legal representatives. The SCAnDi network will meet regularly to ensure the technical deliveries of the research remain aligned with the needs of the Criminal Justice Systems across the UK and beyond.

SCAnDi was awarded £624,387 by the Economic and Social Research Council, part of UKRI. Work is set to start in April 2024 and expected to last a year.