the principle in digital data forensics as well as other forensics fields called "locard's principle" states that: $$ a$.$ crime scenes always require fencing off $$ b$.$ data has to be frozen, and duplicated perfectly in order to properly use in a court of law o c$.$ logging information about the chain of custody is mandatory. $$ d$.$ there is always some change to an environment or space after a crime is committed, or somebody trespasses.