premise: Although the authorities are not saying who the suspect is, all of the attention so far has fallen on James C. Kopp, a 44-year-old anti-abortion protester who had been traveling around the country from demonstration to demonstration for years.
  Officially, Kopp is being sought as a ``material witness'' in the case.
  Clark said it was easier to seek extradition of an indicted suspect from another state or a foreign country than of someone wanted as a material witness. For now, though, that would be a theoretical advantage since the authorities have admitted they have no idea where Kopp is.
  Clark said there was ``no question'' that the finding of the rifle was important in his decision to seek an indictment. The rifle was discovered April 8 buried one foot below the ground, about 200 feet behind Slepian's house. It is undergoing testing at the FBI laboratory in Washington, but the authorities have said it resembles the kind of high-powered rifle used in the slaying.
   Why is the rifle undergoing testing?
hypothesis: the finding of the rifle