Why isn't DNA seen as a valid source of Halachic decision making? Is it because it's too small for the naked eye? A margin of error problem? What?
Normally, physical evidence is plenty of information to make halachic decisions off of. For example, a piece of unmarked meat found in a Jewish neighborhood is assumed kosher, because it's in a Jewish neighborhood. And the gemorah responds, to the person who says he wished he had a drawing tablet to draw the tzizit of the generation of the desert, by saying that if he had just memorized it in his head, that would have been good enough!
Source for the question: http://www.jewishpress.com/pageroute.do/49607
Some of the authors in Contending with Catastrophe recount that several rabbis deliberated at length concerning the reliability of DNA evidence in identifying dead bodies or body parts (with a few even coming to the conclusion that it cannot be relied upon exclusively). Isn't the reliability of DNA evidence a well-known fact that was settled by scientists and statisticians a long time ago? How is it that rabbis in 2011 are spending their time on this matter? Don't their actions give ammunition to those Jews who argue that rabbinic leaders are behind the times?