Hakuba had certainly been in close proximity to Kaitou Kid often enough to have taken note of the distinct scent of cosmetics that hovered around him. It wasn't all that surprising, really, considering the thief's (admittedly well-deserved) reputation as a master of disguise. He had also been in close proximity to one Kuroba Kaito often enough, when he knew the other boy wouldn't have had time for his usual rigourous scrubbing routine to notice the same scent about him.
It was really a grave misfortune, Hakuba always thought, that olfactory evidence wouldn't stand up in court; that cosmetic scent was highly distinctive, and not one that most men – or even most women, for that matter – carried about them. The worst part though, was how in his more irrational moments, it seemed sometimes that Kuroba was positively gloating about it. Most of the time of course, Hakuba knew that this wasn't so; Kuroba had an… enthusiastic personality, but even out of 'character' he was too much a gentleman to openly gloat about something so petty.
Still, sometimes Hakuba really wished that olfactory evidence was admissible in court. He would have a field day.