Obtaining Reference Samples: •Standard/reference sample—Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene evidence. •The examination of evidence, whether it is soil, blood, glass, hair, fibers, and so on, often requires comparison with a known standard/reference sample. •We can only use a hair found at the crime scene if we have hair to compare it to. •Bloodstained evidence must be accompanied by a whole-blood or buccal swab •Buccal swab- swab of the inner portion of the cheek preformed to collect cells for use in determining DNA profile of an individual
•Some evidence is accompanied by substrate controls. •Substrate controls – Uncontaminated surface material close to an area where physical evidence has been deposited; used to ensure that the surface on which a sample has been deposited does not interfere with laboratory tests.