One avenue of investigation is already closed off to forensic officials working the Boston Marathon bombing case due to efforts dating back decades by the National Rifle Association and gun manufacturers.
... a crucial piece of evidence called a taggant that could be used to trace the gunpowder used in the bombs to a buyer at a point of sale is not available to investigators.
“If you had a good taggant this would be a good thing for this kind of crime. It could help identify the point of manufacturer, and chain of custody,” Bob Morhard, an explosives consultant and chief executive officer of Zukovich, Morhard & Wade, LLC., in Pennsylvania, who has traced explosives and detonators in use in the United States and Saudi Arabia, told msnbc.com. “The problem is nobody wants to know what the material is.”
Explosives manufacturers are required to place tracing elements known as identification taggants only in plastic explosives but not in gunpowder, thanks to lobbying efforts by the NRA and large gun manufacturing groups.
... In the past, the NRA has argued that taggants could affect the trajectory of bullets and would also be a de facto form of weapons registration....
