premise: Kopp also has been linked, through DNA testing, to a strand of hair found near where the sniper fired, law enforcement sources have said.
  Nicknamed the ``Atomic Dog'' in anti-abortion circles, Kopp had been arrested in several states since 1990 for protesting abortion. His car was spotted in Slepian's neighborhood in the weeks before the shooting, and was found abandoned at the Newark, N.J., airport in December.
  The filing of the charges has intensified interest in Kopp as a suspect in three non-fatal sniper attacks on Canadian abortion providers, and one near Rochester, N.Y., between 1994 and 1997.
  Kopp is now the second anti-abortion activist being sought by the FBI as a suspect in a fatal attack.
   What actions from the law enforcement could lead to the filing of the charges against Kopp?
hypothesis: through DNA testing