BlogOfHolding.com posted this fantastic breakdown on how D&D spells change the nature of criminal investigations. See http://blogofholding.com/?p=6850 for more and support Paul’s efforts.
Local tier (level 1-4): Towns, baronies, local thieves guilds, low-level casters, monsters with caster minions.
Locate Object (level 2): Pretty much the only way to find a thief in this tier is cast Locate Object on the stolen item. With a range of 1000 feet, though, it will take a while to catch a thief even in a small town.
Tier Analysis: If you’re a petty outlaw, you’re pretty safe, magically speaking. Just hide the stuff more than a mile away from town and it will never be magically found.
Regional tier (level 5-10): City-states or small countries, duchies, crime syndicates, big merchant houses, noble families, drow houses.
Clairvoyance (level 3): Its range is a mile, and it’s pretty much a room-by-room search, so its uses are limited to surveillance of known suspects.
Sending (level 3): You can’t locate someone with Sending, but you can send them threatening messages or offer them deals. If your pursuers’ highest spell level is 3, prepare to be mildly irritated by daily telepathic threats. It’s basically all they can do to you.
Divination (level 4): Ask a question about something to happen within 7 days. It’s hard to see the utility of this spell for catching enemies, and the answers are cryptic anyway.
Locate Creature (level 4): Like Locate Object, it only works within 1000 ft.
Commune (level 5): At level 5, divination spells start to get more useful. Commune lets you ask three yes/no questions, so you can use it to play a really slow game of 20 questions about the target.
Contact Other Plane (level 5): Like Commune, but five questions, and it’s way too dangerous to use every day (chances of death or insanity with every casting). Sensible NPCs probably won’t use this spell much.
Dream (level 5): You can’t locate an enemy but you can threaten them, do psychic damage, and prevent them from resting. You might be able to kill them at a distance without ever finding them.
Scrying (level 5): Almost certainly the spell of choice for hunters of PCs. The PC gets a saving throw, with a bonus if the caster doesn’t personally know the target, and a penalty if the caster has physical evidence (like fingernail clippings). Organizations should have CSI-like crime squads to track down such evidence. Even if the target makes the save, the spell is repeatable every day. On a success, the caster can see the target’s surroundings (for 10 minutes) but doesn’t necessarily know the global location.
Tier Analysis: PCs who upset regional authorities can expect regular angry Sendings and Dreams, and daily scry attempts which will eventually succeed unless the PCs take countermeasures. The PCs should avoid recognizable surroundings like the Eiffel Tower. Scrying gives the DM a new problem: exactly when do the enemies try to tune in? while the PCs are discussing their plans, or while they are mutely trudging through anonymous forest? Here’s a DM trick: set a phone alert for, say, an hour into the game session. When it goes off, that’s when the enemies try to scry.
Major tier (level 11-16): Major countries, major religions, major campaign villains, major worldwide organizations.
Conjure Elemental (level 6): This is a level 5 spell, but cast at level 6, it can summon an Invisible Stalker. The Stalker automatically knows the direction and distance to the target. Even without the stalkers’ assassination abilities, that’s bad news for fugitives. And a new stalker can be summoned every day.
Teleport (level 7): Finding the fugitive is all well and good, but Teleport or Tree Stride (level 6) let you go out and get them.
Tier Analysis: Compared to the regional tier, major-tier organizations are slightly better at finding you, and way better at taking you out. Between Invisible Stalker and scry-and-die teleport tactics, you can’t escape – except by going to another plane of existence.
World-spanning tier (level 17-20): Global or planar empires, demon princes, Sauron-level villains.
Gate (level 9): Costs 5000 GP per casting, but it’s worth it. If the caster knows the targets’ names, and they’re on a different plane, it will summon them (unless they’re in the demesne of a deity or similar creature). Combine this spell with Plane Shift (level 7) to guarantee that you’re on a different plane of existence from your target.
Tier Analysis: Gate takes away fugitives’ extraplanar bolt holes. Only the gods can hide them from 9th-level casters.