A total of 320 prints taken from 5 donors (4 males and 1 female) were applied to porous and nonporous samples, and the deposited prints were allowed to age for at least 1 week prior to irradiation exposure. The prints were cut down the center, with one-half designated either as a control or as an irradiated sample. The random nature of this assignment limited the potential impact of left or right pressure bias when the prints were deposited. The exact radiation dose and conditions are not reported in this paper for operational security reasons. Two types of porous substrates were used: Xerox Premium Multipurpose 4024 paper and white, blue-lined paper. Three types of nonporous substrates were used: a clear polyvinyl chloride based plastic, clear plastic Ziplock-type bag, and a black colored polyethylene based garbage bag material. The results show that the irradiation process apparently has a significant impact on the visualization of latent prints on treated surfaces, with only a few exceptions. The two colloidal techniques, physical developer and multimetal deposition, both produced results that were at least comparable, and in some cases superior to the results obtained from the control samples. Overall, there were significant differences in results observed with different donors and surface types. The results indicate that despite all the variables that can affect outcomes for latent print visualization, the general result of irradiation is that some level of damage occurs to both the substrate and the latent print. 14 figures and 16 references