"Hold up," said Nguyen, raising her hand. "Is this one of those things where once you tell me, I'm going to have to call Vargas back so you can tell him, too?"
"Definitely," Andrea said firmly.
"Then stay here, I'll drag him in," she said, disappearing back out to the roof.
Kyle and Andrea stood in silence for a moment.
"Do you think Gusev smokes?" Kyle asked.
"I guess I only saw him the once… He wasn't smoking then," Andrea said. "Why?"
"Just wondering if one of the cigarette butts up there belonged to him," Kyle mused.
Physical evidence placing him at the scene would be helpful, but… "Even if he does smoke, I think he'd hold off while actively committing a murder. I assume he's smart enough to not leave obvious DNA lying around at a crime scene."
"I've convicted criminals who left dumber evidence than that, even ones who should know better," said Kyle.