Identify the father of a baby as early as the eighth week of pregnancy . The new method, reported in the New England Journal of Medicine , uses fetal DNA isolated from the mother's blood. The test has already been used to prove an affair in a murder trial, and experts say it has other significant medical and legal applications. "The technology is extremely important and really a very, very significant step forward for medical prenatal diagnosis," says Peter Benn, PhD, director of the diagnostic medical genetics laboratories at the University of Connecticut Health Center in Farmington. He was not involved in the research. A previous study by the same researchers showed how the test could be used early in pregnancy to determine whether a fetus has Down syndrome , for example. "That technology will allow genetic disorders to be identified without going through amniocentesis or chorionic villus sampling . That's a very important and useful step forward b...