Identifying criminals from a single cell

The latest techniques in genetics can identify an individual from just one cell.

A new project is set to explore whether the justice system could use these to create DNA profiles from complex crime scene evidence.

Led by the Earlham Institute, a consortium of researchers including a team from the University of Portsmouth, has been awarded nearly £625k to work with experts across the criminal justice system.

They will be exploring 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) will examine whether new techniques in the single-cell analysis field could add valuable new DNA evidence to investigations when used by forensic investigators.

Shedding cells

Humans shed cells wherever they go, and these cells 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 and 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. Investigations potentially lose information about the cell type or origin of the cell. Mixed samples can also considerably reduce the success of searches against DNA databases.

This means it can be more difficult to piece together a clear story of how an event took place, or to ensure justice is delivered for a victim and also for an accused.

Analysis

Single-cell analysis allows genomes to be constructed from considerably much smaller amounts of genetic material. It is often used to explore differences between individual cells in mixed samples. The technique 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. The 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 Iain Macaulay, Technical Development Group Leader at the Earlham Institute, is leading the SCAnDi project. He 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 who, how, when, and why the DNA ended up at a crime scene."

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.

He added: "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."

Complex mixtures of cells, both baseline data and those mimicking crime scene samples, will be obtained for analysis by Dr Katherine Brown from the University of Portsmouth, Dr George Zouganelis from the University of Derby, and Dr Nick Dawnay from Liverpool John Moores University.

Cell mixtures will be catalogued and divided between institutions for various analyses, including standard human DNA fingerprinting, but also innovative next generation amplification and sequencing methods to ascertain what DNA can be obtained and whether we can determine its origin.

Dr Katherine Brown, Principal Lecturer in Forensic Science in the School of Criminology and Criminal Justice at the University of Portsmouth, said: "The SCAnDI project is revolutionary and I am proud that the University of Portsmouth is a partner. It puts the School of Criminology and Criminal Justice at the forefront of innovative ideas and research that underpins our investigative processes. The project builds our research and teaching capacity, expertise and student experiences, preparing our graduates for the fast-paced environment that is forensic science."

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