Any physician. However, it depends on the type of situation. In a difficult homicide, it is good to have two or more pathologists, one or more with specialty board in forensic pathology. If it's a death in hospital / with disease, often you're best with a general pathologist like me. The law specifies who orders the autopsy, and this varies from place to place (coroner, medical examiner.).
Forensic pathologist. Either a forensic pathologist or a coroner. Forensic pathologist must be board certified in pathology, and is usually (but not always) subspecialty certified in forensic pathology. For coroners, in locations that can use them, the qualifications vary by jurisdiction. Usually they have to be physician, but sometimes they can even be a layperson (who should get assistance from a pathologist).
Forensic pathologist. A forenisc pathologist is specially trained to do autopsies from private, medical deaths to homicides and suicided.