Question

a. describe what presumptive and confirmatory tests indicate about possible blood samples, and explain why you will perform both tests on the samples from the scene.

Explanation:

Presumptive tests give a quick indication if a sample may contain blood, often using color - change reactions. They are useful for rapid screening at a scene. Confirmatory tests, like immunological or DNA - based tests, provide definitive proof of the presence of blood and can also identify the source (human or animal etc.). Performing both ensures accuracy. Presumptive tests may have false positives, so confirmatory tests are needed to validate the results.

Answer:

Presumptive tests give a quick indication of possible blood presence (e.g., through color - change), useful for initial screening. Confirmatory tests provide definitive proof of blood and can identify its source. Both are performed because presumptive tests may have false positives and confirmatory tests validate the results.