Digital Evidence. If a computer is the fruit or instrumentality of a crime, the investigators will focus on the hardware. If the crime involves contraband information, the investigators will look for anything that relates to that information,
Computer technology is evolving rapidly but the fundamental components and operations are relatively static. A central processing unit starts the basic input and output system, which performs a power-on self test, and loads an operating system from a disk. Rules of evidence also remain fairly static - distinguishing between hearsay and direct evidence and requiring proof of authenticity and integrity.
So like the officer had said, in an investigation, the nature and extent of the search will depend on the known circumstances of the crime. If a computer is the fruit or instrumentality of a crime, the investigators will focus on the hardware. If the crime involves contraband information, the investigators will look for anything that relates to that information, including the hardware containing it. If information on a computer is evidence and the investigators know what they are looking for, it might be possible to collect the evidence needed quite quickly. Swift searches are necessary in exigent circumstances. If the information is evidence but the investigators do not know what they are looking for, then either a lengthy search of the computers involved will be required or it might make sense to collect everything and search it later in a controlled environment.