CSI: NY2004

Detective Stella Bonasera:
If you're looking into the Alissa Danville case for mistakes, I expect to be consulted.

Detective Mac Taylor:
I wasn't looking...

Detective Stella Bonasera:
Mac, the murder weapon was in the alley with his DNA on it. What else did you expect to find?

Detective Mac Taylor:
Well, for one, we didn't take a substrate control sample on the murder weapon.

Detective Stella Bonasera:
That's because Sullivan claimed that the hammer wasn't his. In that kind of a case, not taking a control sample is standard procedure.

Detective Mac Taylor:
Well, maybe that should change, because finding someone's DNA on a murder weapon shouldn't automatically make them guilty.

Detective Stella Bonasera:
It doesn't. Let's just consider the facts in this case, all right? His coworker testified that every time Alissa Danville walked past the construction site, Sullivan stopped and watched her go by. Then there's the hammer. It was issued to every employee of Luxwell Construction Company. Every single hammer was accounted for except for Quinn Sullivan's. And yet he claims that the hammer we found at the crime scene with his DNA on it wasn't his.

Detective Mac Taylor:
He told me it was.

Detective Stella Bonasera:
You went to see him.

Detective Mac Taylor:
Mm-hmm. He now claims the hammer, but he still sticks to his story that he didn't kill Alissa Danville.

Detective Stella Bonasera:
You believe him?

Detective Mac Taylor:
I want to. Stella, if the hammer was his, his DNA could have already been on it. DNA from epithelials he shed from normal, everyday use. Source attribution, Stella. It's a viable possibility the victim's blood was spattered on top of Sullivan's epithelials. When we tested the blood for DNA, we got a match for both the victim and Sullivan.

Detective Stella Bonasera:
Well, if we had known that it was Sullivan's hammer, it wouldn't have changed our test results.

[Mac gives Stella a look, and realization dawns on her]

Detective Stella Bonasera:
But it might have changed our conclusion.