In order to become a forensic pathologist you must go to Medical School and obtain your M.D. No Ph.d available in order to become a forensic pathologist as the Ph.d is more for research style positions.
Afterwards complete residency and specialized training which can take an additional 4-5 years plus fellowship and after that you have to pass a state exam in clinical and anatomical pathology then you can become a board certified forensic pathologist
But don't let the amount of time discourage you, im guessing that if you were going for a Ph.D it won't but it looks like a rewarding and extremely interesting job