A forensic expert says there's no evidence that a machine gun carried by an Idaho soldier caused the death of an Afghan civilian in January  2010.  Private 1st Class Andrew Holmes of Boise is one of five soldiers from Joint Base Lewis McChord south of Seattle charged in the thrill killings of three Afghan civilians last year. Holmes is accused of directly participating in the first killing.      Spc. Jeremy Morlock, who has been sentenced to 24 years in the case, claimed to have thrown a grenade at the first victim as Holmes shot the man with a powerful machine gun. But Dr. Michael Baden, the chief forensic pathologist with the New York state police, testified for the defense during a hearing Monday that after reviewing photos of the victim's body, he could find no evidence of any machine gun wounds.      The judge said he would agree to allow such expert testimony at Holmes court martial.      Holmes' attorney says that's important because if his client had really been involved in a murder  plot, he would not have missed with a machine gun from such a short distance.