'Walking Tall' sheriff likely murdered his wife in 1967, Tennessee officials say

[Sibelius Fan]

9. Unreliable

The wax/diphenylamine test, also known as the paraffin test, was a now-obsolete forensic technique used to detect gunshot residue (GSR) by applying melted wax to a suspect's hands to create a cast. This wax cast was then treated with a chemical solution of diphenylamine and concentrated sulfuric acid; the presence of deep blue flecks, indicating nitrates, would suggest recent firearm discharge. However, the test was found to be unreliable due to false positive results from other sources, including fertilizers, and the ease with which residue could be removed by washing.