forensics

noun, plural in form but singular or plural in construction

fo·​ren·​sics fə-ˈren(t)-sikz, -ˈren-zikz 

: the application of scientific knowledge to legal problems

especially : scientific analysis of physical evidence (such as evidence from a crime scene)

In forensics, DNA is extracted from fluids or tissue found at a crime scene, often sperm or seminal fluid from the bodies or clothing of rape victims, or blood found at the scene of violent crime.

—Christopher Joyce and Eric Stover, Witnesses from the Grave