The lowest number of ridge counts on the developed latent prints was obtained using the SPR I (0) and SPR VII (0) developers, and they could not be used to detect latent fingerprints on any type of the tested surfaces. SPR I contained 10% (w/v) molybdenum disulfide in 0.8% (v/v) tergitol NP-7, with a particle and detergent proportion of 10 and 0.8%, respectively, and a ratio of particle to detergent of 12.5. SPR VII contained ferric oxide suspended in tergitol NP-7 which could not be dissolved completely and precipitated and so fogged the background. Indeed, it has been reported before that too many particles will fog the background and too much detergent or detergent itself will degrade the latent print.(4) Thus, the percentages of Fe3O4 particle (10), detergent (0.8) and particle/detergent (12.5 g/ml) of SPR VII were similar to those in SPR I.