The medical examiner is an appointed official in some American jurisdictions who is trained in pathology that investigates deaths that occur under unusual or suspicious circumstances, to perform post-mortem examinations, and in some jurisdictions to initiate inquests. In the US, there are two death investigation systems, the coroner system based on English law, and the medical examiner system, which evolved from the coroner system during the latter half of the 19th century. The type of system varies from municipality to municipality and from state to state, with over 2,000 separate jurisdictions for investigating unnatural deaths. In 2002, 22 states had a medical examiner system, 11 states had a coroner system, and 18 states had a mixed system. Since the 1940s, the medical examiner system has gradually replaced the coroner system, and serves about 48% of the US population. The coroner is not necessarily a medical doctor, but a lawyer, or even a layperson. In the 19th century, the public became dissatisfied with lay coroners and demanded that the coroner be replaced by a physician. In 1918, New York City introduced the office of the Chief Medical Examiner, and appointed physicians experienced in the field of pathology. In 1959, the medical subspecialty of forensic pathology was formally certified. The types of death reportable to the system are determined by federal, state or local laws. Commonly, these include violent, suspicious, sudden, and unexpected deaths, death when no physician or practitioner treated recently, inmates in public institutions, in custody of law enforcement, during or immediately following therapeutic or diagnostic procedures, or deaths due to neglect. Duties A medical examiner's duties vary by location, but typically include: investigating human organs like the stomach, liver, brain, determining cause of death, examining the condition of the body studying tissue, organs, cells, and bodily fluids issuing death certificates, maintaining death records, responding to deaths in mass disasters, working closely with law enforcement identifying unknown dead, or performing other functions depending on local law. In some jurisdictions, a coroner performs these and other duties. It is common for a medical examiner to visit crime scenes or to testify in court. Medical examiners specialize in forensic knowledge and rely on this during their work. In addition to studying cadavers, they are also trained in toxicology, DNA technology and forensic serology (blood analysis). Pulling from each area of knowledge, a medical examiner is expert in determining a cause of death.