Flash Cloning is a medical process used by humans to clone body parts. The process uses a sample of a human's DNA to grow a cloned organ, which can then be transplanted into the subject that contributed the DNA sample. Usually, the organ is programmed to grow at an accelerated rate and cease rapid development when transplanted into the subject. This makes the method viable in urgent situations, where patients can't afford to spend years waiting for a normal organ to develop. Since the transplanted organ's DNA matches that of the recipient, the risk of transplant rejection is almost completely eliminated.
While Flash Cloning entire humans is possible, it is by no means perfect, and unauthorized cloning is illegal. The crime is punished harshly, and is considered to have a severity on par with that of modern day child pornography. The process involves the modification of a human embryo, which causes it to develop one hundred times faster than it would have naturally. Many anomalies appear because flash clones are forced to develop too quickly—they lack the muscle memory and socialization of their hosts. Though these problems can be corrected with intensive therapy, the worst flaw in flash-cloned humans—compounding biological defects—cannot be corrected. One to two months after cloning, a flash-clone will start to degenerate from metabolic instability as part of a process called "metabolic cascade failure". They inevitably die from various neurological and physiological diseases.
Flash-clones were used in the SPARTAN-II Program. After the Spartan candidates were abducted from their homes, they were replaced with flash-clones as part of a cover-up to draw away suspicion. The flash-clones quickly died natural (though certainly abnormal) deaths, drawing suspicion away from ONI. One example was Daisy-023's flash clone whom she discovered after escaping from the program. Daisy-023's clone later died of Metabolic Cascade Failure. Internal criticism of the unethical use of flash-clones led to the use of orphaned children in the subsequent SPARTAN-III Program.
Conversation Between Daisy-023 and her Flash Clone
Flash Clone: "Sometimes, I have this dream. Always the same dream. I dream I'm strong, stronger than anyone. Like you, just like you are. Here. I want you to have this."
*Much to Daisy's astonishment, her flash clone holds out a teddy bear that she had lost seven years ago when she was abducted.*
Daisy-023: "But why me?"
Flash Clone: "I don't know, to be honest with you. I just, something tells me that I should. I want you to take it." *Daisy-023 accepts it with a smile.*
This conversation potentially reveals several things about flash cloned humans. First, it seems that they are, in every way, just as alive as ordinary humans. One thing to be noted, is that the flash clone smiles throughout the majority of the exchange. They possess emotions and have mental processes every bit as complex as our own. It might also imply a form of telepathic link between the clone and the original, at least in a one-way fashion.
Usage for creating A.I
Because humanity is a Tier 3 civilization and the creation of a "smart" A.I requires the destruction of a human brain, the brain of a deceased person is often used. There is one known exception in the Halo Universe however: Cortana was modeled after an unauthorized flash clone of Dr. Catherine Halsey's brain, thus illegal in the UNSC. The use of a clone allowed the UNSC to provide a brain used for the mapping of the AI's "mind" with no undue effects on the donor.