A major crime scene investigation may start the same way in every case, that is by first on-scene officers doing a preliminary search of the scene for victims and suspects, then protecting evidence until it can be properly documented and collected, however every scene is unique unto itself.
Think of a thousand different scenarios; that’s what’s waiting for you when you cross under that barrier tape, and go into the secured scene.
The processing of a crime scene is a long, and very detailed – and every detail is important.
You’re going to start by getting some basic information from officers first on the scene, and with their insight taken into consideration, your next step is to make your own observations. Every detail you see has the potential of being a lynchpin in the investigation, so everything has to be done slowly and methodically.
Marking obvious pieces of evidence, sketching the scene, taking photographs, processing the scene for fingerprints, or for blood evidence, and the later collection of any physical evidence that could point to hat happened at the scene, with the hopes of eventually linking the evidence to a suspect is the paramount goal at this point.
Typical crime scenes are only in TV, real world scenes may have you fingerprinting a point of entry at a home invasion, collecting bloody clothes at the scene of a stabbing, searching for hidden (latent) blood at the scene of a murder scene, or trying to collect hair and fiber evidence from a carjacking victim’s vehicle interior.
The ultimate goal is the successful prosecution of the suspect, so every move must be thought out in advance and carefully performed, always mindful to preserve any collected evidence so you or a second party lab can have unadulterated evidence to examine and test, thus eliminating issues in later court proceedings.
Most every agency will handle the division between field work and lab work differently. For instance, a CSI might only process the scene itself, with all follow up examinations being done by investigators performing in house testing, or all but the most simple of follow up work might be sent to an outside lab.
By definition, what is done at the crime scene is called crime scene investigation with Laboratory work is considered forensic work. Some agency’s investigators perform both tasks in differing degrees, however almost all but the basic laboratory examinations will be forwarded to a forensic scientist, either from the agency’s lab, or an outside lab. These labs typically perform chemical examinations, DNA examinations, tool mark examinations, and other highly specialized tasks.
Crime scene investigations bring legal knowledge, common sense, experience and science together.