Detection of Latent DNA Using a DNA Binding Dye

Latent DNA can be deposited every time a person holds or touches an item. This "touch DNA" can be crucial evidence if the item is of forensic significance. Until very recently, there were no means to visualize this DNA. The advent of using a dye that binds to DNA has opened up this possibility. The application of the dye is simple to perform, and a mobile microscope allows rapid visualization of the cellular material, even in ambient light. The dye can be applied in a solution of either 75% ethanol or water. As this is a solution-based dye, the application works best on non-absorbent surfaces.DNA within cellular material, such as dead skin cells, appears as green dots under 50X magnification; zooming to 220X magnification confirms that these are cells. The location and number of these cells can be photographed allowing a record of the presence of otherwise latent DNA.This chapter details the processes involved in the detection of latent DNA using Diamond™ Nucleic Acid Dye with both control samples (that act as very effective training samples) and the staining of evidential items. By developing skills in determining cell locations, a targeted approach to crime scene collection is now possible.