The importance of determining the chemical composition of tape adhesive prior to conducting fingermark enhancement: a preliminary study

Adhesive tape is a challenging substrate for fingermark enhancement. A range of enhancement techniques are available for the adhesive side of tapes, with powder suspensions commonly used. The ability of powder suspensions, particularly iron oxide (FeO), to enhance fingermarks is known to be affected by adhesive compositions. Knowing the adhesive composition of a tape exhibit would therefore assist the examiner in choosing the most suitable fingermark enhancement technique, but the chemical composition of tapes is not currently considered by fingermark examiners. This research demonstrates the use of Fourier Transform Infrared Spectroscopy (FTIR) to assist decision-making before fingermark enhancement on the adhesive side of tapes. FTIR was used to chemically classify the adhesive composition of 50 tapes, identifying four adhesive compositions. The performances of FeO and carbon powder suspensions were compared for the enhancement of fingermarks across the four adhesive compositions. Results supported literature observations that FeO performance was impacted by acrylic-based adhesives due to background development. However, FeO was found to outperform carbon powder suspension on all other adhesive compositions examined. Classification of adhesive sides of tapes is therefore a beneficial initial step which can be achieved non-destructively with FTIR rather than spot testing samples, as is currently recommended.