Prosecutors say the accused Boston Marathon bombers used Christmas lights, toy car parts and powder from firecrackers to make the deadly explosive devices that ripped through crowds of spectators last year.

Newly-released court documents indicate Dzhokhar Tsarnaev and his now-dead brother would have likely been unable to build the pressure cooker bombs without assistance or training.

The explosions killed three people and injured more than 260.

The 20-year-old Dzhokhar is in federal custody awaiting trial.  (Metro Networks Inc.)