The attorneys for Stephen Marc Stone want their client to have a mental evaluation.
The attorneys filed the motion on Thursday.
Police said Stone strangled his wife, Krista, and strangled and drowned their 7-year-old son, Zachary, in their home on Chickamauga Trail in Huntsville back in February.
According to court documents, the defense claims Stone suffers from mental illness and mental deficiency.
No word yet on when the judge will rule on the motion.