i don't understand why the damn >> reporter: detectives larry kuczkowski and t.k. waters showed us what happened when they ushered derrick into his tv room. >> so we're standing here and we asked derrick, can you turn on the tv? so derrick comes in here. >> reporter: why? why did you ask him to turn on the tv? >> well, we had never, the tv wasn't on when we got here and we had found all of the remotes on the sink so we just wanted to see how it worked. changed the input to the dvd player, up comes the menu for a porn video. at that point, i start shaking my finger at it and going, that's not mine. there's no way that's mine. and there's no way kim would be looking at that. and i look at the dvd player. and i'm going, that's your murderer. that's going to be who was in my house. >> reporter: that's a creepy clue. >> as soon as i knew that, i knew they were going to be able to get him. they were going to be able to find out who did this to my wife. >> it was one of those moments where the hair would stand up on the back of your neck. because to have that video in the

. >> reporter: detective larry kuczkowski interviewed derrick, still in his firefighter uniform. he said the husband seemed willing to answer all his questions, starting with how >> okay, so you left the house yesterday morning, probably -- >> about 7:10. >> your shifted started at 8:00 a.m. saturday? >> yes. >> did you go back home for any reason? nothing like that? his alibi at that point is that he's at work. and he does work for the fire department. they work 24-hour shifts, they start 8:00 in the morning, they work till the following morning at 8:00. >> reporter: a story that would be easy enough to check out. next, the detective asked derrick how he'd found kim when he got home from work. >> i go in, just go straight to the bedroom, and i opened it up. there, she's not laying down, she's on the damn the floor. >> did you touch her or anything? >> yeah. i touched her. i turned her over. i think she was on the right side. >> he was upset. you know, did he break down? not as much as i think some people would, you know, telling the story about what they just came home to. >> i