Flash cloning

Flash Cloning is a medical process used by the UNSC whereby human body parts are cloned. This usually involves a sample of a subject's DNA which is used to grow a clone of an organ or body part, which can then be transplanted into the subject where the DNA came from. This way, organ transplants are faster and easier and the rate of success is far higher. Usually the organ is programmed to grow at an accelerated rate, then to cease rapid development when transplanted into the subject. Therefore, the organ grows quickly and functions properly and efficiently. Since the organ contains the same subject's DNA, there is no threat of rejection by the body.

Human Cloning
Flash cloning humans is imperfect, and it is illegal for someone who is unauthorized to flash clone. Doing so would result with severe and harsh punishments for violators and is comparable to modern day child pornography in terms of severity. An embryo is taken and developed a hundred times faster than it would have naturally, becoming something different than it would have been. Many anomalies appear because flash clones are forced to develop too quickly. Flash clones have none of the memories of their hosts, including the natural behavioral training most humans get observing people while growing up. They can be trained with intensive therapy, but after a month or two, they start to degenerate from metabolic instability in a process called "Metabolic Cascade Failure" until they die from various neurological and physiological diseases.

After the future SPARTAN-IIs were kidnapped from their homes, they were replaced by flash clones, intended to explain the sudden disappearance of the Spartan-II candidates. Though the flash clones quickly died, they had succeeded in their purpose to draw attention away from ONI and therefore drawing the attention away from the kidnapping.

Further in Fall of Reach it is said that John-117 is flash cloned another three times during the Human-Covenant War.

Usage for Creating AIs
Flash cloning was also used in the creation of the AI Cortana. Being that Dr. Catherine Halsey's brain was still quite functional, a flash clone was made for the rather destructive AI creation process which consequently fried the cloned brain.