All forensic scientists will need to major in an applicable subject, such as chemistry, biology, biological anthropology, sociology or law enforcement. In addition, you will need to take classes that cover each of those sub-fields, so that you have experience in biochemical lab work and criminal investigation.
Many labs will require additional degrees, and forensic anthropology programs offer the most competitive masters and doctorates. Included in these degrees will be training in lab work, human osteology, evidence collection, law enforcement protocols and even expert witness testimony skills.
Other specializations are available if you are not interested in working directly with corpses, and will require additional degrees. These may include physics or engineering degrees for ballistics, biology degrees for DNA analysis, and even PhDs in toxicology, computer composite art, spore and pollen analysis or criminal psychology.