I was wondering this exact thing. In fact, it seems to me that the light would have come on when the killer walked through the fence and cut the screen. If Darlie or the boys had been awake, they might have seen him in the backyard.
She also could have seen him on his way out if she just looked out the kitchen window. The way she describes the distance between them, she probably reached the point to see out of the kitchen window just as he was leaving through the garage window. No way to miss that movement in the yard if the floodlight is on, but Darlie described everything as dark except for the light from the TV.
What I wonder is how the killer had the opportunity to even see the open window when you can't see that window unless you go in the backyard, which is surrounded by what looks like a 8ft fence. Could be higher, I don't know. You can't see through the fence, so how likely will a killer risk opening the gate or jumping the fence when a security light just came on JUST so he can check for open windows while the light remains on? Plus, how does he know it was an automatic light if someone turned it on because they saw him? Awfully risky if you don't even know there's access to the house back there.
If the light stays on 15 minutes, the light would have been on from the moment the killer was in the yard to enter the house until the moment he left. I don't know if the light adds time if it experiences more movement or not.
The crime probably took 5 minutes -- if that much. I say that because Jodi Arias killed Travis Alexander three different ways in under 2 minutes.
The first cop got there at about almost 4 minutes into the 911 call. He did not testify to seeing a light on in the driveway. But he was not asked, either.
The neighbor across the street who saw Darin outside when the first cop arrived did not mention the driveway floodlight being on either. Again, he was not asked and didn't volunteer any information about it.
I have not read the testimony of other cops yet, but the first cop, went half way into the kitchen, saw the utility door to the garage closed, and did not go any further until the second cop arrived. He didn't indicate that he looked out the kitchen window or saw anything unusual or lit up outside, either.
Upon the arrival of the second cop, which I believe was about almost 6 minutes into the 911 call and at its conclusion, the two cops checked the garage and then went and checked upstairs. They said it was dark in the garage. The garage has a ton of windows and no curtains. At roughly 11 minutes after the killer first got there, wouldn't they have seen a floodlight coming into the garage?
The second cop went outside after searching upstairs. The search could not have taken four minutes, so the cop should have seen a light on still. I have not read the second cop's testimony yet to see what he says about the light.
Did you guys know that house had an alarm system? Yep. Sure did.
