Determining the chronology of deposition of natural fingermarks and inks on paper using secondary ion mass spectrometry

This study thoroughly explores the use of time-of-flight secondary ion mass spectrometry ({ToF}-{SIMS}) for determining the deposition sequence of fingermarks and ink on a porous paper surface. Our experimental work has demonstrated that mapping selected endogenous components present in natural fingermarks enables the observation of friction ridges on a laser-printed surface, only when a fingerprint is deposited over this layer of ink. Further investigations have shown limited success on ink-jet printing and ballpoint pen inks. 51 blind tests carried out on natural, latent fingermarks on laser-printed surfaces; up to 14th depletion with samples aged for up to 421 days have resulted in a 100\% success rate. Development with ninhydrin was found to affect the fingermark residue through mobilisation of ions, therefore sequencing determination was compromised; whilst iodine fuming and 1,2-indanedione developers did not. This implied that selected development methods affected success in fingermark-ink deposition order determination. These results were further corroborated through inter-laboratory validation studies. The adopted protocol and extensive series of tests have therefore demonstrated the effectiveness and limitations of {ToF}-{SIMS} in providing chronological sequencing information of fingermarks on questioned documents; successfully resolving this order of deposition query. This journal is ?? the Partner Organisations 2014.