Currently, when we stealth, members of our own alliance can still see us.
I expect once the PvP aspects of the Justice System go live we'll be invisible to player guards.
Will we also be invisible to non-guard players as well?
If we are not invisible to everybody, we'll have non-guard players working in tandem with the player guards giving away our positions via tell or teamspeak or even zone chat, since their non-combatant status will make them untouchable, so the guards can approach and break stealth either with proximity or detect potions.
Don't missunderstand, if our stealth is broken in the normal way by getting too close or when someone pops a detect potion, it would make perfect sense for a 'concerned citizen' to do the equivalent of "Stop thief!". I think it will cause problems if everybody not currently engaged in Justice System PvP can see us crouched.
I'm hoping that stealthed players will be invisible to anybody they aren't grouped with. All the normal rules would apply, get too close in the line of sight and we are revealed.