In many cases today, however, forensic samples come instead from “touch” DNA—miniscule samples of DNA deposited on physical surfaces that people have touched. Touch DNA is less reliable and harder to match both because it may not include enough DNA for meaningful interpretation and because it often contains DNA from multiple persons—some of whom may have had no connection to the crime at all. With touch DNA, lab analysts may see a match where none exists.
So long as the notion of reasonable doubt is upheld, by law enforcement, prosecutors and in court, this is not an issue. If its upheld by the court then touch DNA will not be enough. However, if it gets to court that can be enough to ruin an innocent person's life. There are some very dire consequences here, particular since soon it will be possible to run DNA testing for even routine crime.