Catherine Halsey

Catherine Elizabeth Halsey, M.D., Ph.D. is a civilian consultant (#409871) (Civilian Identification Number 10141-026-SRB4695) to the United Nations Space Command Office of Naval Intelligence. She is a biological scientist, medical doctor, and an expert in computer systems.

Early Life
Dr. Halsey is portrayed as an extremely intelligent and gifted woman, who, by the age of 15, was already working on her second doctoral thesis. It can be inferred that she had already completed undergraduate studies and her first doctorate by this age.

ONI Projects
Dr. Halsey made huge contributions to many Section 3 projects including the creation and deployment of Artificial Intelligence constructs (such as Cortana). She created the Spartan-II project as well as the development of the MJOLNIR Armour Systems.

The SPARTAN-II Project
Dr. Halsey was the person responsible for both the SPARTAN-II project, and the MJOLNIR project. She, along with Captain Jacob Keyes (then a Lieutenant, Junior Grade), handpicked the first candidates for the SPARTAN-II program, and secretly brought them to Reach.

On Reach, she trained the Spartans along with Chief Petty Officer Mendez and the AI Deja. She supervised their augmentation procedures, combat training, education and studied the effects of the Spartan lifestyle on the children. She kept in close contact with them all throughout their lifetimes, from her base under Reach. Annoyingly to the Spartans, she was always able to tell them apart from each other, even under half a ton of MJOLNIR battle armor. Dr. Halsey always used their first names, never their ranks or Spartan ID numbers.

Fall of Reach
After the Covenant's invasion of Reach, Dr. Halsey volunteered to remain at ONI's CASTLE Base to destroy all the data that ONI had left behind. Fortunately, surviving SPARTAN-II soldiers found her and they were able to escape with the Forerunner Crystal ONI had been protecting.

Escape into the Unknown
Dr. Halsey later saw the importance of destroying this artifact, for it was too dangerous and uncontrollable to use. After escaping Reach, she stole a small spacecraft and, along with sedated Kelly-087, escaped into slipspace. Her whereabouts were unknown until the events of Ghosts of Onyx.

The Good Doctor returns
In Ghosts of Onyx, Dr. Halsey and Kelly eventually make it to Onyx, while reuniting with Chief Petty Officer Mendez and eventually her remaining SPARTAN-II soldiers. She helps decipher the mystery of the planet.

Halsey's Guilt
Dr. Halsey carried extraordinary guilt because of the SPARTAN-II project, and she felt that she had exploited the children and destroyed their lives. Though she continued to support them and gain monumental prestige for her efforts, she also felt responsible for each one who died. She never could quite justify their exploitation as a "necessary sacrifice". This likely accounts for her actions in abducting Spartan-087.

Appearances

 * Halo: The Fall of Reach
 * Halo: The Flood (mentioned)
 * Halo: First Strike
 * Halo: Ghosts of Onyx