In police work, what does “obtaining samples from a known standard” mean?
When police investigate a crime, they often pick up physical evidence. They might, for example, find hair or blood. They might find a bullet that has been fired. They might find latent fingerprints. The problem is that they do not really know where these pieces of evidence came from. These are, at this point, pieces of evidence from unknown sources.
What police want to do is to obtain samples from “known standards.” These are samples that are directly taken from a source by the police. For example, the police could physically take a blood sample or a hair sample from a person. They could take the person’s fingerprints. These would be samples from known standards. The police have direct knowledge of the origins of these samples.
Samples whose source is known ...:
A [known] standard/reference sample is material of a verifiable/documented source which, when compared with evidence of an unknown source, shows an association or linkage between an offender, crime scene, and/or victim (e.g., a carpet cutting taken from a location...) (National Institute of Justice)
Samples from known standards are important because they can be compared with unknown evidence. The unknown evidence can then be proven to come (or not to come) from that particular known standard. This will, of course, help the police to determine who has committed a given crime.