An evaluation of the effect of incorporating metal salts into 1,8 diazafluoren-9-one (DFO) formulations for fingermark enhancement.

A study into the modification of 1,8-diazafluoren-9-one (DFO) formulations by the additions of metal salts into the working solution is reported. Similar additions have been found to increase the fluorescence of marks developed using other amino acid reagents including 1,2-indandione and the ninhydrin analogue 5-methylthioninhydrin. It was found that adding zinc chloride to give a 1:1 ratio of zinc ions:DFO molecules gave optimum fluorescence, and improvements in performance over the standard DFO formulation were achieved. Attempts to produce equivalent formulations with iron, nickel and palladium chlorides were unsuccessful. In a comparative trial with a 1,2-indandione-zinc formulation on brown paper and cardboard substrates, 1,2-indandione-zinc gave superior results and it was decided to focus further research on this reagent instead of DFO-zinc.

A validation study of the 1,2-indandione reagent for operational use in the UK: Part 2 - Optimization of processing conditions.

This paper contains details of work carried out to identify the most effective processing conditions for the optimized 1,2-indandione/zn formulation developed for use under UK conditions. Using direct measurements of fluorescence taken from test spots of amino acids and eccrine sweat during oven processing, complemented with experiments on real fingermarks, it was established that processing temperatures above 120°C in the oven were detrimental to the fluorescence of the developed mark. Alternative methods of development to oven processing were found to be effective, but less controllable. High levels of humidification were also found to be detrimental to the fluorescence of 1,2-indandione developed marks, and oven processing at 100°C and 0% relative humidity is therefore recommended for further studies. It has also been shown that 1,2-indandione can develop fingermarks at temperatures as low as 20°C, making it a candidate for use at crime scenes.

A validation study of the 1,2-indandione reagent for operational use in the UK: Part 1 - Formulation optimization.

This paper contains details of work carried out to examine the composition of 1,2-indandione formulations and to develop the most effective 1,2-indandione/zinc formulation for use under UK conditions. Previous research into the reactions of 1,2-indandione without zinc ions have concluded that formulations containing methanol produce stable hemiketals, which are less reactive to amino acids, resulting in reduced fluorescence intensity of developed fingermarks. In this study, fingermarks were treated using varying formulations of 1,2-indandione, with and without the presence of methanol and zinc ions. It was found that both were beneficial in producing marks of the highest fluorescence intensity, although too much methanol could have a detrimental effect on the quality the mark due to diffusion of ridge detail. Therefore the 1,2-indandione formulation recommended for further trials has been modified to contain both zinc ions and methanol.