A victim of a crime (or his descendant, if the character is dead) can authorize a single copy of a summonable scent from a crime committed against him. Only an authorized scent can be used to summon a criminal.
When proper scent decay is implemented, authorized scents shouldn't expire. This is necessary to make proper trials possible. I think an average trial would take several RL days, and scents would disappear before a verdict is made. If a single copy of a scent could be kept (the authorized one), it would be possible to summon the criminal after the trial.
Now, thieves may cry foul. Yes, I agree that tracking is currently unfair towards thieves, mostly because scents are forever. But there's a load of difference between keeping a dozen copies of a scent, and keeping just one. It's hard enough to track with a single scent, but when you have to conserve it so you actually have uses left for summoning, it can be a huge challenge. In fact, it may be downright impossible to track down a thief across two supergrids with just one scent.
And that last bit is where the real beauty of this is. A thief that leaves just one or two summonable scents (let's say a vandalism for knocking down the wall and theft for actual theft) will be very hard to track. But a thief that ransacks a whole town and leaves dozens of scents will be trivially easy to track down and kill. This encourages sustainable theft, and makes life easier for producers and thus pickings better for the thieves.
Oh, and this requires that looking into a container leaves just trespassing, and taking out items leaves one theft per item.