Fingerprints have been the most powerful means of biometric identification for over a century. However, the process has remained largely unchanged in scope as only the physical characteristics of the ridge pattern are exploited to compare a crime scene mark with a fingerprint record, a process that leads to suspect identification if a match is found. Nonetheless, current fingerprinting may fail as in the case of smudged, partial and/or overlapped marks, or no fingerprint record. 

A new technique

In 2008, the Fingerprint Research Group (FRG) at Sheffield Hallam University led by Professor Simona Francese, initiated the development of Matrix Assisted Laser Desorption Ionisation Mass Spectrometry Profiling/Imaging (MALDI MSP/I) based methods for the chemical profiling/imaging of fingermarks (molecular fingerprinting), as well as their translation in an operational environment. 

Molecular fingerprinting enhances the forensic value of the fingermark evidence by detecting and visualising the molecules that can be found within, including contaminants, naturally occurring and introduced into the body. Molecular fingerprinting enables a novel way to conduct criminal profiling and to inform crime scene management, narrow down the pool of suspects and speed up investigations. 

The ridge pattern can be reconstructed through visualising the molecules that are detected while preserving the integrity of the evidence (Figure 1). 

The technology can provide ridge detail additional to that obtained by conventional CSI techniques in high spatial resolution (Figure 2).

Identifying a suspect

Higher likelihood of suspect identification can be achieved through:

• Stitching/superimposition of multiple molecular images from the thousands of molecules simultaneously detected (improving ridge pattern coverage/continuity).
• Separating overlapping fingermarks by individually recalling images of molecules that are uniquely distributed in each overlapping mark (Figure 3). 

The FRG pursued the recovery of personal and lifestyle information around the fingermark's owner and/or on their actions prior to or during committing the crime, enabling:

• Determination of the sex of the suspect from their fingermark peptidic/protein composition.
• Recovery of intelligence on the use of condoms, enabling associative/probative evidence in the context of crimes of sexual nature.
• Detection and mapping of drugs. 
• Specific and multi-informative detection of blood in marks/stains, compatible with CSI techniques.

Shaping the future of forensics

Since 2011, the applicability of molecular fingerprinting to crime scene investigation has attracted funding and research-shaping input from the Home Office, the Defence Science and Technology Laboratory (Dstl), West Yorkshire Police and the Netherlands Forensic Institute. 

As a result, molecular fingerprinting has been used in operational casework in the UK and overseas as well as being incorporated into Home Office/Dstl edited Fingermark Visualisation Manual, and promoted to Cat B in 2022, due to its high technology readiness level (TRL).

Molecular Fingerprinting at the intersection with clinical diagnostics

Fingemarks contain a plethora of biological molecules that are both sweat and migrating from the blood stream to sweat glands. We have discovered that protein profiles of breast cancer patients differ according to their staging. In particular from a swipe of a fingertip, using a combination of proteomics, MALDI MS and artificial intelligence, we can distinguish benign patients from early breast cancer women and metastatic patients with the 98% accuracy (Russo et al 2023 https://doi.org/10.1038/s41598-023-29036-7). We now intend to extend these studies to a larger pool of women.