Bear with me, it's not what it seems. It has been proposed before to create some connection between scents, such as a 'scene'. It occurs to me that it's really just not that important where the crime occurs. If you go through the trouble of connecting an individual character's scents from one location and another within a time frame window then the 'evidence' is really rather 'equally incriminating'. If there are not such social relationships to establish that an individual is committing crimes in multiple locations then kudos to that badass who should naturally benefit from such RP'd stealth. Anyway, it could be as simple as picking up a scent and right clicking on another. They can even evolve into combo scents depending on the severity of the crime. Rates shouldn't allow the 'combo scent' to decay any less slowly and should still retain the nature of all the scents added to it. You might have to have the skill and spend a point on it (through and action on its flower menu or whatever) to verify owner and be capable of noting that particular scent's similarity to any other that has likewise so been analyzed (and maybe even run another skill check like psy, ha)
In the end the player who is benefiting is the ranger by having more inventory and more tracking capability reflecting that character skill and the loser is he commits more crimes. Also, this creates a method of dispute resolution and also creates the possibility of memorizing a scent in order to identify the character the nexrt time you smell them on your screen. I'm not sure how well a person could describe a scent to another person, but i imagine it'd be similar to the requirement to smell them in the first place (Ala psy as i suggested, or *whatever* makes sense).
It doesn't really solve any major problem other than identifying criminals and making inventory management for dealing with them a lot easier.
It might sound horrible if you abstract it as actually putting the scents together and not as it reperesting the act of camparison and the denotation that these small thing taking up inventory is less due to their size then their mental value which becomes more condensed as they are compared and so they take up less space to sort and identify them individually.
It might even be an object that requires you to store the scents in with leather wool or linen or silk (as progressive capacity) and not making them reusable.