What process is the fastest way to produce copies of dna?

PCR, polymerase chain reaction, is the fastest way to artificially (in a laboratory) multiply few copies of DNA into many, in order to create enough of a sample to use for other genetic testing.

It is used quite often in forensic science, such as magnifying a small recovered sample of DNA from body fluids or tissue samples at a crime scene, into a vastly greater quantity of DNA for identification of suspect (s) or victim (s).