Of the nine chemical warfare (CW) agents that were included in the study, hydrogen cyanide, sarin, sodium fluoroacetate, and diazinon did not inhibit the recovery of human DNA from blood. Four of the CW agents: chlorine, phosgene, dimethyl sulfate, and lewisite I prevented a full profile from being obtained. These four agents were shown to inhibit the recovery of DNA. The chemical reactivity of dimethyl sulfate and lewisite I suggest that alkylation of the nitrogen bases is the most likely route for the destruction of DNA in their presence. For the successful recovery of physical evidence from contaminated scenes, the effect of the decontamination agents on the evidence must be investigated. If decontamination agents are shown to affect an examiner’s ability to extract and profile DNA, then DNA recovery must be performed prior to decontamination. This research study considered the effects of the Canadian Aqueous System for Chemical/Biological Agent Decontamination (CASCAD), MDF LSA-100, and nine CW agents on blood found at the scene. Bloodstains were contaminated with nine CW agents and then decontaminated with CASCAD and MDF LSA-100 according to manufacturer instructions prior to DNA extraction and profiling.