MALDI imaging of blood and blood provenance in old fingermarks

Reliable confirmation of the presence of blood in stains and marks is crucial to reconstruct the dynamics of a violent crime. MALDI MS Profiling (MALDI MSP) and MALDI MS Imaging (MALDI MSI) have been shown to be suitable confirmatory tests to this effect [1-4]. However, additional and important information is based on the attribution of the source of blood (animal or human), as a few murder cases in the public domain demonstrate. The Fingermark Research Group at Sheffield Hallam University, recently published on the validation of a MALDI MSP method to detect and distinguish between human and animal blood (down to the animal species level) in enhanced blood marks and stains analyzed in a blind fashion [5] (Figure 1). Here we use a combination of bottom-up proteomics and MALDI MSI to visualize blood of bovine or human origin in 4-year-old fingermarks. These are unused marks originating from the batch of blind samples on which the Kennedy et al. publication [5] was based.