Difference Between a Detective and a Crime Scene Investigator (CSI)

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:

  1. 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.
  2. 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.
  3. 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.

Article written by Radek Gadek

Radek holds a Master’s degree in Criminal Justice from Boston University. He is currently doing consulting work and runs this blog to provide relevant information on criminal justice degrees, colleges and related careers.

10 comments… add one
  • Ryan Kennedy


    I live in Massachusetts and I know the processes done at a crime scene are abnormal when compared to other states. Basically I am a freshmen in college in Massachusetts as well, majoring in “crime and justice studies”. Not exactly criminal justice because it isn’t offered. Anyways, I basically want to find out all the types of people that visit crime scenes in Massachusetts,and who gets paid the most. I love the fact of visiting crime scenes and might be pushing to the csi route instead of the detective, I don’t want to be cop and I am hoping that a csi might get paid a little bit more. I just don’t know exactly what a csi in MA does because there aren’t fresh crime scenes every day, so do they just run tests in labs all day when not at scenes? Anyways, I know a crime and justice studies bachelors won’t get me anywhere in the csi field so should I double major in both that and a hard science like biology? I am almost 19 and have this year to decide what classes I am going to take next year as I focus on my major or two majors. Thanks.

    • Radek M. Gadek

      The Crime and Justice Studies degree is a great alternative to a Criminal Justice degree. In fact, many schools offer nearly identical curriculum but name the program differently.

      A crime and justice degree is going to help you with the CSI scene, despite what you’ve read or heard. That said, it is wise to take courses/major that leads towards the CSI career field. I would speak with local CSI labs about opportunities to do internships. Internships tend to open doors and give one so much inside information where it may help you assess your need to, or need not to, take a double major. If there are no internships, I would call law enforcement / CSI agencies in your area to schedule a meeting. You would be surprised how many people in our industry are willing to help. I always try to offer some sort of incentive when asking for such a meeting; lunch will usually do it : )

      Good luck

  • shataya young

    i woulld like to know if ryan was ever part of any of these perfessions?

  • Matthew

    I am looking for the career that apprehends suspects, and interrogates. I am wondering if this would fall under a detective or a crime scene investigator?

    • Radek Gadek

      It would be the detective career track.

  • Mia

    Hi I’m 15 and I want to be a csi without having to be prepared to shoot anyone. Do you have to be a cop to be a csi? Are the crime scenes dangerous? I really don’t want to shoot anyone. Please help!

  • Roma

    Hi Im Roma

    Im interested in putting together the pieces of a cases and finding out who did it or searching and gathering information at the crime scene like fingerprints and so on soo what group would these fall under please let me know!

    • Radek Gadek

      Right before the word “or” is the detective and after the word “or” is the CSI.

  • Brenda

    I am not decided what I would like to go into (CSI or Detective) so should I go or masters or bachelors. And also how are you able to know if you can go into the CSI, in the terms of family members having issues with the law, but you do not live with them will that affect your career?

  • Zach

    I’m interested in the field of some sort of crime investigation, though I don’t quite know the differences between each job field. My main want for the job field would be a type that would go to the crime scene, collect evidence, and look to and prove how it connects to the suspects. I understand these may be separate jobs entirely, and if that’s the case I would like to know the individual ones, but I do remember seeing “Criminalist” which fits that description, though looking at crime scene investigation, detective, criminal investigation, and forensic science, I’m not sure which one not only pays the best amount but also fits that type of job description the best. Could you explain to me the differences of each with what they do, along with the pay differences? If that’s too much to answer, is there anything you can link me to to possibly answer that?

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