Abstract
Forensic biological evidence has a dual identity: it is an evidential substrate that must be protected from contamination and, in some circumstances, a potential source of occupational biological exposure. This focused narrative review addresses two linked questions: how occupational exposure changes as evidence moves from crime scene to DNA laboratory, and how that risk can be controlled without compromising evidence integrity. The synthesis is organised around three distinctions: DNA relevance is not the same as infectious-risk relevance; pathogen detection is not equivalent to viable infectivity; and the presence of a biological hazard is not the same as an effective exposure or transmission event. Selected bloodborne, airborne, respiratory and sharps-related hazards are used to illustrate how evidence state, handling task, exposure route and control effectiveness interact across collection, packaging, receiving, examination, DNA pre-processing, storage and disposal. Experimental and postmortem evidence shows that drying, decomposition, refrigeration and elapsed time cannot serve as universal indicators of biological safety, although persistence data should not be translated directly into casework transmission probabilities. A pathway-based control model is proposed in which engineering and work-practice controls, personal protective equipment, vaccination, training, incident reporting and post-exposure pathways are integrated with evidence-preservation requirements. The principal evidence gaps are forensic-specific: denominator-based exposure data, compromised-package incidents, concealed sharps, aerosol-generating pre-analytical tasks and engineering-control evaluations remain poorly quantified.