Three FBI experts say they found four types of explosives and other chemicals when they tested items found in Colorado theater shooting defendant James Holmes' apartment.
The experts testified Tuesday at a pretrial hearing to determine whether they will testify at Holmes' trial. They shed little new light on the case and mostly answered questions about testing methods.
Holmes pleaded not guilty by reason of insanity to charges of killing 12 people and injuring 70 in the July 2012 attack.
Prosecutors and defense lawyers are arguing over evidence that could be used to weaken his insanity claim, including homemade bombs found in his apartment.
Police have said the bombs were intricately planned and were meant to divert officers from the theater. Prosecutors could cite that as evidence Holmes was sane.