Consistency and reproducibility in the deposition and evaluation of latent fingermarks, contributing to an investigation into the effectiveness of a portable cyanoacrylate fuming system and aluminium powder for latent fingermark development

There are a variety of techniques that can be used for the development of latent friction ridge skin marks. Most of these techniques can only be used in a laboratory because of the requirement for specialist equipment, and health and safety implications. One exception is powder dusting, which is an established and very commonly used technique for the development of friction ridge skin marks on non-porous surfaces at scenes of crime. Cyanoacrylate fuming is another effective method for the development of friction ridge skin marks on non-porous surfaces. There have been a number of attempts to devise ‘in situ’ cyanoacrylate fuming methods, and recently Foster and Freeman Ltd. have introduced a portable cyanoacrylate fuming system, which can be used at the scene of the crime known as the SUPERfume.

A comparison of the effectiveness of the SUPERfume with the powder dusting technique for the development of latent fingermarks was undertaken. This involved the use of several non-porous surfaces that are commonly encountered on immovable or large items at scenes of crime. A total of 13500 latent fingermarks were deposited onto these surfaces using a fingerprint sampler, which was a device manufactured specifically for this research project. The fingerprint sampler facilitated the reproducible deposition of the fingermarks under controlled conditions of force application, the angle of friction ridge to surface contact and the duration of friction ridge to surface contact. The latent fingermarks were stored in five temperature controlled environments for periods of up to fifty two weeks. They were then developed using the portable cyanoacrylate fuming device (SUPERfume), in a specially designed ‘SUPERfume room’, or using the aluminium powder dusting method. Of these 13500 fingermarks 5400 were assessed using a specially designed grading system, which was based upon the results of primary research with a number of leading fingerprint experts and research departments. A statistical analysis of the data using a variety of tests was conducted.

The main findings from this research were that latent fingermarks deposited onto glass surfaces were generally of a higher quality than latent fingermarks deposited onto very smooth surfaces, such as enamelled metal paint and smooth plastic. Textured surfaces including textured plastic and varnished wood produced latent fingermarks of a relatively poor quality. Latent fingermarks deposited onto glass, enamelled metal paint and varnished wood were developed more effectively with aluminium powder than cyanoacrylate fuming using the SUPERfume. Cyanoacrylate fuming (SUPERfume) was more effective at developing latent fingermarks deposited onto smooth and textured plastic surfaces.

Generally as the temperature of the storage temperature was increased the quality of the fingermarks decreased. This observation was more apparent for latent fingermarks developed using aluminium powder. In instances where latent fingermarks were stored in very warm environments (37°C) cyanoacrylate fuming using the SUPERfume was more effective at developing the marks than aluminium powder. Following storage temperatures between -10°C and 20°C aluminium powder developed latent fingermarks of a higher quality than cyanoacrylate fuming using the SUPERfume. There was some evidence to suggest that storage temperatures cooler than 0ºC were detrimental to latent fingermark quality, but only one temperature below 0ºC was considered. There was no difference in the quality of the fingermarks developed using aluminium powder or cyanoacrylate fuming (SUPERfume) for fingermarks stored at 20°C.

As the length of storage time increased the quality of the latent fingermarks decreased. This was more noticeable for fingermarks developed using aluminium powder compared to cyanoacrylate fuming (SUPERfume). It was possible to develop usable fingermarks on most surfaces after fifty two weeks of storage, in all temperature environments, using both development techniques. In general aluminium powder was found to be more effective at developing latent fingermarks compared to the SUPERfume for fingermarks less than twenty weeks old. Following twenty four weeks and fifty two weeks of storage there was no difference in the effectiveness of aluminium powder or cyanoacrylate fuming (SUPERfume) for the development of latent fingermarks.

Taking into account all surface types, storage temperatures and storage time periods aluminium powder produced fingermarks of a higher quality compared to the cyanoacrylate fuming technique using the SUPERfume.