Feds believe that Dylann Roff was 'self-radicalized' in the months before the attack in which he shot nine black churchgoers in Charleston last year.
The information filed Monday was part of a list of more than a dozen expert witnesses that prosecutors intend to call in Dylann Roof's federal death penalty trial later this year.
The government believes that Roof's actions were "consistent with the concept of leaderless resistance and martyrdom advocated by white supremacy extremist groups and self-radicalization leading to violence."