Before you can say, "He's evil!" Horatio and Sevilla are out at the Caplin place, where a remarkably resilient Jason Caplin is holding one of his children without attempting to kill her -- something of an aberration, given recent events. He then takes Horatio for an insurance adjustor ("they're pulling up the flooring in my house because it's rotted with blood"), and after he gives a spiel of woes that does not once mention any deep or profound sense of bereavement for the three children or wife who were slain, Horatio cuts him off with, "Blood is why we came today. We want to talk about your blood on your baby." Erin squeals, and after calming her down, Jason's all, "I bled on my baby? I got shot. I guess my blood must have been everywhere." Horatio explains that actually, it's the gravitational droplets of blood that were the problem, as "that proves that you were standing over him while you were bleeding." Long story short: Luke died protecting Max from Jason; after a standoff in which Jason correctly surmised that Luke wouldn't shoot him while he was holding Max, Luke managed to get Max and head toward the door, where Jason, unencumbered by anything so pesky as concern over Max's life, shot Luke in the back a few times.
After that rather dull denouement, Jason's bundled into the back of a squad car, where he begins making excuses. "I never slept!" I believe it was Calleigh who wasn't buying it as an excuse back when everyone instantly suspected Stephanie of postpartum psychosis; let's hope she's as harsh here. Jason carries on some more about how the burden of his family drove him mad. At this point, I'm so disgusted with the heavy-handed manipulation throughout this episode (when in doubt, arouse the audience's pity and fear by showing a cute child in trouble) and asinine judgments flung toward Stephanie, I end up snarling at the screen, "It's called birth control, or it's called put up and shut up." I mean, really. What was he expecting from four kids -- the next Von Trapp Family Singers? After the car bearing the shifty and evil Jason drives off, Sevilla asks, "Did he just confess?" Horatio bursts her bubble with, "He was laying the groundwork for his defense." "Insanity," Sevilla guesses. Horatio nods, "Two-pronged: I didn't know what I was doing, and I certainly didn't know it was wrong." Sevilla thinks Jason might be onto something. Determined to make sure it doesn't, Horatio sets out to prove her wrong. After a few moments alone with Jason's shirt and a micropipette, we find out how: there's ammonia on Jason's shirt, and a log of him calling home shortly before driving back. Those two things establish that he had removed all his prints from the gun cabinet by means of the ammonia, then called Stephanie to check on the cabinet -- thus getting her to plant her prints. That sort of premeditation undercuts the I-suddenly-snapped defense.