“What the detective story is about is not murder but the restoration of order.”- P.D. James. The point of a detectives existence is to protect the innocent from cruel people with dark intentions. Their job consists of researching, tracking, and piecing evidence together like a jigsaw puzzle until they all fit together to create a clearer picture. They take long periods of time and dedication in order to gather whatever information they can to prevent criminals from harming citizens.
Detective and police organizations look similar and have similar purposes, however, over time they improved and advanced with the new developing technology. Earlier when detective agencies were first invented, They did similar things differently. What I mean by this is that, for example, back then when they didn't have the same technology that we have today, they had to investigate the best they could with all the evidence they could possibly find at a crime scene like prints or trace evidence with the lack of a skilled forensics team because they didn't have the complete ability to fully analyze the evidence evidence.
Different types of investigators do different things. For example Private Investigators , or PI's, will investigate anything without question, for a price. There are also many types of private detectives such as Legal, Corporate, Workman's, and Cyber PI's whom of which, all do various things. They all use similar methods of detection however.
More physical crimes can leave behind major traces of evidence like shoe/finger prints. These can possibly determine the identity of a criminal or their general appearance. Sometimes luminal tests are taken at a scene to catch any prints or substances at a crime scene that could have been missed. Luminal test's use a certain type of light to locate translucent liquids, gases, and prints that are not possibly visible to the naked eye.