Obviously, forensic psychiatrists are psychiatrists and forensic psychologists are clinical psychologists. Psychiatrists go to medical school (4 years) and receive all the normal general physical medicine training required to receive the MD degree. You will then a do a residency in psychiatry, which is 4 more years in length. Depending on how dedicated you are to forensics by that time, you will do a fellowship in forensic psychiatry after residency. On the other hand clincial psychologists receive a Ph.D or Psy.D in clinical psychology, where you will focus exclusively on psychopathology, psychometric assessment of cognitive functioning and personality/emotional functioning, as well as psychotherapy. The Ph.D is a research degree also, so you will get a heavy dose of stats, research methodology and will write a full dissertation in addition to your clinical training. Most of the time, all this training will 4 to 5 years. You will then complete a 1 year full time internship, before officially being awarded the doctorate. Again, depending on how dedicated you are to exclusively doing forensic cases, you may need to take a post-doc for additional training in forensics. Over half of recent doctoral grads are taking post-docs now in something these days. However, if you know at the outset that forensics is your game, I recommend applying to a university that has a clincial forensic specialty track within their clincial program, and to do forensic oriented practicum placement while in training.
The job description of a forensic psychiatrist vs. forensic psychologist will be quite different, although they are often called to give the same types of decisions/opinions (i.e., competency) in a case. However, a psychiatrist will always be the expert in anything medically related that maybe affecting the patient's mental status, and will be the one consulted for decisions about psychopharm interventions. Clinical neuropsychologists (many who specialize in forensic applications of neuropsych) are being pulled into court frequently these days to give opinions as to the cognitive status of individuals, and for the assessment for malingering of neurocogntive deficits and/or psychiatric illness. In addition to clincial interviews, psychologists will utilize standardized psychometric tests of cognitive and emotional status to help answer these questions and refine diagnostic impressions. These tests are also very useful when there is likelihood that the individual in question may be exaggerating or outright faking psychiatric illness in order to get out out of a crime. Psychiatrists are NOT trained in psychometric assessment, so this is something that is a unique contribution of the psychologist.
You will always make more money in forensics being a psychiatrist, as they have the almighty MD and can demand larger salaries/billing. However, forensics can be a very lucrative specialty for either profession. However, with all that money comes headaches, stress, and legal liabilities that are unique to this specialty. I have seen psychologists get pulled in to court over many different things, and I assure you, it gets nasty very fast. Lawyers are ruthless, and you're constantly being pulled in 3 different directions at once. Basically, it looks like a huge headache and I am planning to stay OUT of court in my practice as much as possible. You should also be aware that while you can make good money, it takes a while to build up the reputation so that lawyers will be calling you and asking for your advice/consultation. You will need a more traditional employment setting such as a private practice or working at a hospital while the years tick by and you build a rep. A good "forensic psychologist" is a "good psychologist" in general, so you will need to have an active practice and have seen plenty of patients. You will need to keep up to speed on the research literature and keep up on your reading (so lawyers dont make you look like an out-of-touch ass on the stand). If you really want your phone ringing off the hook, you should optimally be a researcher too and have pubs in a certain area. That way, lawyers know you're the one to go to for that particular area. The best and most well know forensic psychs are "battle seasoned" clinicians so to speak, who have built reps over many years.
