The scientists fabricated blood and saliva samples containing DNA from a person other than the donor of the blood and saliva. They also showed that if they had access to a DNA profile in a database, they could construct a sample of DNA to match that profile without obtaining any tissue from that person.
http://www.schneier.com/blog/archive...ating_dna.html
A link to another paper:
Researchers have demonstrated it's possible to remove all the DNA from samples like blood and saliva, and replace it with genetic material from a different individual—even when the only source of this material is a used cigarette butt. Their methodology was good enough to fool a lab that does crime-scene DNA testing.
http://arstechnica.com/science/news/...search-lab.ars