In fingerprint analysis, which of the following reflects a source of heat application?

The application of heat in fingerprint analysis serves important purposes, particularly in the development and enhancement of latent prints. An alcohol lamp is a source of heat that can be used to speed up chemical reactions or to activate certain processes during the fingerprinting technique. For instance, when using certain powders or chemical treatments, applying gentle heat can help improve the visibility and quality of the latent print.

In contrast, the other options do not relate to heat application in the same way. Ninhydrin is a chemical reagent used to develop latent fingerprints on porous surfaces, often reacting with amino acids in the fingerprints but without the need for heat. Freon 113, a solvent, is used in some fingerprint processing methods, primarily for cleaning or dissolving materials, but it does not provide heat. Magnetic powder, typically used to enhance prints on non-porous surfaces, relies on magnetic properties rather than heat application. Thus, the use of an alcohol lamp is distinctly linked to heat application in fingerprint analysis, aligning perfectly with the question's requirement.