Who has jurisdiction over crime scenes in real life?

Question

How do they decide who works a crime/homicide? You have homicide detectives (Law and Order), Crime Scene Investigators (CSI), the FBI (Numb3rs), US Marshalls(US Marshalls), et al. On TV, they all basically do the same thing, but who does what in real life?

Answer 1

In real life, a officer/deputy arrives the scene. He/she secures the scene, and writes the initial report.
If there is evidence to be collected, such as at a homicide, he/she then calls for a crime scene technician (some of the larger departments have CSTs and Investigators/Detectives but in most of the smaller departments the same person is the CST and the Investigator).
At this point, the officer/deputy normally has little to do with the rest of the investigation. The CST will report the results (and, no, it doesn't happen nearly as quickly as on TV--read weeks as opposed to minutes) to the Investigator.
The Investigator (or if it is a big case, a team of investigators) will work the case, running leads and conducting interviews.
If the case crosses into another agencies jurisdiction, that agency will also get involved.
Small agencies will often ask state agencies to assist if the case is very big (homicides).
Once the Investigators find a suspect, they try to obtain as much evidence as possible, then they present it to the District Attorney.
The DA or Assistant DA then decide if they want to prosecute (if the evidence is enough to convict). Then the DA trys the case.

Homicide detectives actually work the cases unless it is on federal property or crosses state lines (the the FBI get involved).
Detectives are often their own CSIs but if they are separate, the CSI just records, collects, and processes the evidence. CSIs do not question suspects.
US Marshalls are generally fugitive recovery and court security.

Answer 2

First the place the crime takes place, and the type of crime.

As soon as the crime first happens, the local police are called.
And the first officer on the scene takes change to start with.
If it is a major crime, each department has rules as to who gets called. If it is a serious crime, first the officers supervisor on duty will be called to the scene, once there he takes over the scene.

Next it will depend ont he deparment, for example in ours, there was no crime scene people, the officers did all of the initial investigation and the officers gather the evidence.

in larger departments, if it is a murder, then the homocide department is called in, they may come to the scene, or they may merely wait for the officers report to come in.
If the officers on the scene want evidence taken ( and they actually have lab techs that come to the field. ( I am sure some departmetns actually have them, but I have never know any personally after 20 years of law enforcement. But there would be techs that do nothing but gather evidence. The actual lab people don't come to the crime scene, they do nothing but work in the lab. And most labs I know of don't work 24 hours a day like on TV either. I guess a few big city labs may.

FBI would normally only be called in, if it invovled counterfiting, terrorists, threats against the president, or some crime they do specific. ( unless you have a small department that requests thier help on some investigation)

But in 90 percent of the deparments, it is the officer who is first at the scene that does most all the work including gathering the evidence and baging it to be sent to a crime lab.

Answer 3

A call comes in about a body being found, a sector car is dispatched to the scene, the officer request a detective the detective on duty responds to the scene, the detective investigates and request CSI, the detective is the person in charge of the scene. In some jurisdictions the prosecutor is called and he becomes in charge but the detective is always the lead investigator. The FBI gets involved if it becomes a federal case. This is how it basically works.