‘Laboratory investigation: search, recovery and analysis’ outlines the various stages of recovering, documenting, and analysing evidence. The first stage of a laboratory investigation is the recovery of samples. As many samples from different investigations share the same laboratory space, care must be taken to prevent contamination. The sample can then undergo a range of tests, and all interactions with the sample are recorded in case notes. A number of biochemical assays exist which test for the presence and source of bodily fluids. It is important when performing and recording such analyses to separate fact (for example from a test result) from the forensic scientist's own opinion.