Besides the items mentioned above you have the options of doing different jobs based on your choice: example do you want to be a detective? do you want to work directly for the police as a laymen? Do you want to work directly for the coroners office? Do you want to be a forensic investigator or only collect evidence? Look into https://www.abmdi.org/. America. Board medicolegal death investigations. You can even start in this area. Where I am as a Forensic Investigator for the Coroners office I am a contractor basically. They want people with a background in Trauma and medicine so an EMT or Paramedic was a great entry point to get my feet in the door. Talk to people to see options. Good luck
I think your best bet would be to look into accredited Bachelor programs in Forensic Science. WVU and Penn State have really great programs - At WVU you can even specialize in forensic investigation. You will have to take coursework in biology and chemistry, however. What is nice about having this degree is that you can do crime scene investigation (work in the field) or work in the lab as a forensic scientist. Also, the International Association for Identification (IAI) website is helpful when looking at jobs, training, and certificate requirements.
If you do not want to get a degree, you could probably start out at an entry level position being an evidence technician and work your way into doing CSI work. However, you will not make much money. Also, the CSI position in Pittsburgh requires a bachelors degree and is pretty competitive. Hope this helps.