Medicine needs at least AAB, and requires Chemistry and usually at least one other science.
THere are Forensic Science degrees, but usually at old poly uni's, and don't require very high grades. THer are elements of all sides of Forensics involved like preparing you to report in a court and criminology and stuff. However I want to be a Forensic Scientist and I was told to do a mainstream chemistry or biology degree, which a speacialist stream in it (eg my degree involves modules in Analytical and Forensic Chemistry). I was told this gives me a better grounding, and more chance of getting into forensics.
You can do a medical degree and become a forensic pathologist (the person that looks at the dead bodoes to find out how they died etc), which I thought would be a really good job (but you would need to have got AAB to go to med school, speand 6 years there, and then a further year as a junior before you became a proper doctor, and would then have to practise as a surgeon before getting into pathology).
Good Luck!!