New Sci 25 May 1996: "Forensic lab awash with Semtex." Just 5 nanograms of RDX -- one of the ingredients in Semtex -- is enough to link a suspected terrorist to a bombing. Yet the DERA forensic laboratory that carries out tests in many high-profile terrorist cases frequently finds more than this on its floor. "It's horrifying," says an independent forensic scientist who specialises in explosives cases. "They seem to have been getting contamination all the time." In contrast, forensic experts frequently say that the Forensic Science Agency in Northern Ireland has the most thorough precautions against contamination. The agency moved to a new laboratory in 1992 after the IRA blew up its old one. SEM_tex