In Turkey, if there is a suspected bag to be a bomb, it is exploded by police. I think everywhere in the world it is like that. What if you put some phosgene or chloropicrin or some gase or tiny particle of something and you call police to say that 'Near place x there is an abandoned bag!'. In fact you don't need to call. Just place the bag to a publicly visible place. Sure somebody will inform cops.
There were at least one 'bomb suspected bag' per day last week in Turkey!
Getting on to subject: When they explode the bag it will be a surprise! Because they just go to take the bag, without any protection. What do you think? Can this be possible?(Spreading made by cops)

It's a clever idea; but keep in mind- when the Bomb Squads come in, they evacuate the area. So if the agent is dispersed, who would it be harming besides the Bomb Squad? Basically, it's effects are very limited. However, if your goal is to kill the Enforcers, then it could be the way to go.

Also, don't the Bomb Squads use X-Rays now, to survey a package before they decide on what to do with it?? Would they not detect some strange liquid?

Now, what if we were to expand on this idea... Instead of Phosgene or Chloropicrin, maybe something very persistent and nasty (like a thickened G-Agent, perhaps). Or, imagine the disaster that would be caused if some radioactive element were placed in a device detonated by the police.

Why not just explode it yourself? It'd be more effective.

Unless your aim is to show the "saviours" the police to be idiots? :)

It'd work in a third world country like Turkey, since they don't use "elite" tools like X-rays prior to blowing something up, including themselves! :D

They evacuate the area but always some curious people around. And they don't use X-ray or anything. If it was informed, you can be sure that it will be exploded. If the air is windy...

Why would they make the bomb explode right near people ? Even if they don't check the bag and detonate it, one can guess they use special places to do it; no more reason why they should use a open air area, close to a town or whatever...

You would need much more gas if you want your bomb to be effective.

And even if the cops are handling the bomb at the time it explodes, I can't see why they would be held as responsible.

Maybe a binary reaction could be used: when the cops take the suitcase, then the reaction occurs, leading to the gas production. I'm thinking in particular to HCN formed with NaCN and acid.
The risk is that someone move the suitcase before the police. But an anonymous call and a slightly hidden placement would help avoiding that.

Yes, that was really clever from the cops, they stand around and handle with it like its only a pack of suggar :D

It would be a good laugh to hear it, but quite difficult to realize. Imagine, you need to find the adequate country, now Turkey will be more suspicious :).
And it certainly would be less easy in the US, for example, which would be even more funny.

Yes, this is an interesting idea. But I feel that somethign like asbestos or radioactive material dispersed by the bomb would be much more effective than most war gasses (which are often prone to thermal decomposition). Asbestos or radioactive material would also have more long term effects (render the area uninhabitable for years, etc), rather than just making a couple of enforcers die and the living ones blush.
And Arthis, I imagine that if they they would detonate the bomb on site if did not know what was in the bomb, as long as it was not in too valuable an area. Consider that some of the self-bombers use AP as thier base charge. Obviously, the cops want to protect their life foremost and are not willing to carry the bomb many km if there is a chance that it could be shock/friction sensitive.