Do you need to hire a forensic science expert witness? The University of Alabama describes what these professionals do:
Most forensic scientists work in a lab doing “traditional” forensic science (DNA, drugs, trace, etc.). Analyzing evidence in the lab requires an undergraduate degree in chemistry, biology, or a related natural science field (like biochemistry, pre-med, microbiology, etc.). The job of a forensic analyst is for the most part limited to lab work (and testifying in court). It is rare that a forensic scientist will be required to visit crime scenes. In some forensic labs, the analysts may assist sheriff’s departments at the crime scene in rural areas, while crime scenes in the city are handled by the city police.
This leads us to the other side of forensic science, the crime scene work. Most often, crime scenes will be processed by licensed police officers trained to be a part of the department’s crime scene unit. Although crime scene technicians will be responsible for the collection of evidence and processing crime scenes, they will not have much to do with the investigation or the analysis of the evidence. Unfortunately, the common portrayal of crime scene investigators (such as the characters on CSI) is a lousy portrayal of the profession since those characters have their hands in all aspects of the investigation and in reality a person will only work in one area (lab vs. crime scene vs. investigation). The fact is, most of the investigation (interviewing suspects and witnesses) is completed by licensed police officers.