In which cases have latent prints developed by heat been used, despite the impractical nature of the technique?

Latent prints developed by heat are particularly useful in arson cases due to the nature of the crime. In arson incidents, surfaces such as walls or furniture may be heated extensively during a fire, often rendering other traditional methods of fingerprint detection ineffective. The heat can cause certain materials (like some plastics or paints) to undergo changes that allow latent prints to be revealed when subjected to heat.

In the context of an arson investigation, it is critical to gather all possible evidence to establish a timeline, identify suspects, or corroborate witness statements. The use of heat to develop latent prints, despite being impractical in many scenarios, can yield valuable evidence that may otherwise be lost, as fingerprints may not be visible or accessible using more conventional techniques. This makes the technique particularly valuable in such cases where other methods fail, changing the dynamics of the investigation.

While latent prints can be found in theft, fraud, or assault cases, the specific application of heat to develop prints during an arson situation stands out as a unique case where this method is prioritized due to the specific conditions produced by the fire.