The 24-year-old's defense attorney has said he'll ask jurors to find Becker not guilty by reason of insanity or diminished responsibility.
Becker had played football for Thomas in high school. He is accused of shooting the coach to death in front of more than 20 students last June 24.
Thomas led the northeast Iowa team for 34 seasons and was the NFL High School Coach of the Year in 2005. Four of his players are now in the NFL.
