Everett Jacobs was a human doctor who was a personal physician in the Office of the President of the Earth Alliance.
Dr. Everett Jacobs was a highly respected physician and expert on xeno-biology. Having traveled extensively throughout the galaxy, he then taught as a professor at Harvard Medical School. One of his students was Stephen Franklin, who studied under him for two years. Dr. Jacobs took time to help Stephen when he was having trouble, and the two developed a close friendship.
By 2258, Dr. Jacobs was working in the Executive Branch of EarthGov, serving as the personal physician to Vice President Morgan Clark (and possibly President Luis Santiago as well). On December 30, 2258, Vice President Clark leaves Earthforce One, claiming to have the flu. A day later the ship exploded at the Io transfer point, resulting in Santiago's death and Clark assuming the President. Dr. Jacobs, having examined Clark personally, learned Clark was not sick at all.
Knowing if Jacobs disappeared too soon it would raise suspicions, Clark kept him close for about six months. He was contacted by allies of General William Hague, who was trying to secure evidence of Clark's complicity in Santiago's death. They arranged for him to escape Earth, but were unable to get him past the Io transfer point because of Clark's agents. He boarded the first ship out, which took him to Babylon 5. Derek Cranston, of Earthforce Special Intelligence, pursued him there with official word being that Jacobs had stolen classified information and was attempting to defect to an alien world.
Jacobs used Stims to help him stay awake, but had no idea of how to escape. He kept a journal of his experiences during this time for his beloved wife in case anything happened to him. He is captured by a man named Max, who realizes Jacobs is on the run. Luckily, Stephen Franklin and Security Chief Michael Garibaldi (who are aware of his true plight) are able to rescue him and recover a Data crystal he had brought along with him containing crucial records of his examinations of Clark. He also renewed his friendship with Doctor Franklin during these events. Captain John Sheridan was then able to arrange for him to stow away in Vorlon Ambassador Kosh's ship and remain undetected by Cranston's team. Cranston left and Kosh's ship returned him to the station, where Hague's operatives managed to then help him escape to safety. 
The following year, once allegations of Clark's complicity had been made public, his evidence regarding Clark's health before the destruction of Earthforce One was put before the Earth Alliance Senate.