Scavenger
Considering the offer of Doctor Destructo, Scavenger looks down at the grate, then to the former supervillain, then to the vent. He considers about the crime scene once more, especially as Matador moments before had told him not to contaminate the scene without the right kit and materials. While the Doctor certainly carries what is needed, the ghoul wouldn't just think once before accepting a mad doctor's offer. Yet Destructo is far smarter than the ghoul is and would probably have been better with finding details than a cop would.
In the end Scavenger sighs and decides not to bother arguing against help. "I suppose we have tampered with the scene enough that we can analyze it without following procedure." He bends his legs down next to the grate. "On the condition that I help. I've done this sort of forensics before. We can find what evidence we need, scan it, and see if we can get any sort of clue or match." Scavenger isn't taking "no" for an answer. He's going to be the saner of the two investigators, at least so the Doctor doesn't happen to miss anything due to how insane the former supervillain is.
Spoiler: OOCI will be assisting Doctor Desctructo in both Gathering Evidence and Analyzing Evidence. This is 2 rolls each using Investigation, right?