To make the fake DNA, all the researchers needed was a small sample of the DNA they wanted to plant (such as that from hair or lingering in saliva left on a discarded coffee cup) and blood from a donor. Donor blood was centrifuged to separate DNA-containing white cells and DNA-free red cells. The researchers then expanded the filched DNA into a larger sample size via whole genome amplification and added it to the DNA-free red blood cells from the donor. Poof! Blood that matched the genetic profile of the person to be framed—not the donor—was created.
Problem is, your average murderer lacks a proper foundation in molecular biology.