The move by attorneys for Julie Schenecker, 50, of Tampa follows last week's announcement by the Hillsborough County State Attorney's office that it would seek the death penalty in the case, The St. Petersburg (Fla.) Times reported.
Her lawyers said Schenecker suffers from " a bipolar disorder with psychotic features."
Schenecker is charged with first-degree murder in the Jan 27 shooting deaths of her 16-year-old daughter Calyx and her 13-year-old son, Beau.
Legal observers said the insanity filing by Schenecker's attorneys indicates the trial will likely be a battle of mental health experts.
Tampa defense lawyer Grady Irvin said her attorneys could make a strong case against the death penalty arguing that their client is a woman already struggling with serious mental problems, trying to raise teenagers with a military husband who was frequently deployed.