Email from Ryan: What is the difference between a homicide detective and a crime scene investigator (CSI)?
A homicide detective and a crime scene investigator are often thought of as one profession. The media, TV, and movies often portray a crime scene where a detective takes a pen out of his pocket and starts poking around the body. You’ll see them lifting a piece of key evidence while there are some other people with cameras and measuring tools all around. Awkward…
The truth is, most detectives and first respondents know very well not to contaminate the crime scene by poking their noses around. The only time you should see a detective around the body is when he or she makes sure if the victim is alive or after the CSI clears them for access. This point will probably be disputed by some in the law enforcement community, but with precious evidence in a form of a foot print or a microscopic particle taking the chance can ultimately demolish the case.
So what is the difference?
For the most part, homicide detectives and crime scene investigators are two different professions, from two different departments. In order to become a detective, you must first be a police officer and pass the detective exam. To become a CSI, you don’t necessarily have to be a police officer. However, there are many departments who train their police officers and detectives to be crime scene investigators, and vice versa. This depends heavily on geographic location and needs of a particular agency.
Smaller municipalities may have a handful of police officers and even fewer detectives. Some of them are trained to process crime scenes when needed, but when a murder case springs up in their community they [should] utilize other impartial law enforcement agencies, like: Sheriff’s Office or State Police.
Why so many professionals?
One big reason of why detectives handling a murder case do not sweep the crime scene for finger prints, hair follicles, and DNA particles is because of the need to have a system of “checks and balances.” Imagine if the lead detective had the responsibility of processing a crime scene:
- It is way too much work for one person to do. As the time ticks away so do the leads that can result in an arrest, or no arrest, of the perpetrator.
- In an event of a mistake an invested investigator can unintentionally or intentionally manipulate the evidence and tests, thus squashing any chance of the case legitimately going to trial.
- His or her career, as well as personal well-being, can be adversely affected through means of corruption and threats.
These are hypothetical examples, but years ago, detectives had a hard task of dealing with crime scenes all by themselves. There were no elaborate CSI units or departments. Detectives did all the leg work, and then some. As praiseworthy as these efforts were, they often were not successful at catching the right suspects, and at times, lead to wrongful convictions and executions. Corruption was common as well.
Crime Scene Investigation units started growing in numbers with the advent of scientific methods for preserving and processing the crime scene. As the number of methods grew, so did the need for well qualified personnel. This way, the detectives could start focusing on the complexities of solving the crime by piecing ALL the pieces together, including those provided by CSIs. Now, many of the CSI careers have components of Forensic Science in them and those have separate sub-fields which further require training and education.
So, to wrap up…
So, if you see a person in a suit and a person in a Crime Scene Unit jacket you can be sure they are working together, but doing completely different work. Although some people may be both a detective and a CSI, you can assume that they are working only one side of the case. A detective collects information processed by the crime scene investigators which is supposed to help them apprehend the perpetrator of the crime. There is much more a detective does behind the scenes that does not include forensic anthropologists and latent print examiners. Both the detective and the crime scene investigator (CSI) careers fall under the criminal justice system umbrella, even the law enforcement field, but should not be considered one and the same.