I wold expect that “Conspiracy To Murder” is a charge that is very difficult to prove. Does it require that the conspirators have written records of their conspiracy? Also, does encouraging someone to commit murder amount to conspiracy?
As an example-suppose an imam in a mosque makes a speech and calls for the murder of someone-is that conspiracy?
Conspiracy can be difficult to prove. Generally, the easiest way is to have some guy testify that he conspired with you, probably because he’s been flipped for a lighter sentence.
But written records, phone taps, financial transactions, and so on can all be used as evidence of conspiracy. New York has a whopping six degrees of conspiracy; here’s how they define Conspiracy in the first degree:
A pretty broad definition that covers a lot of activities that could be involved in the planning of a crime.
ETA: Oops, that’s the definition of second degree conspiracy. First degree requires the involvement of a minor.
ETA2: As for your hypothetical imam, my best guess is that he would instead be charged with something like inciting violence, rather than conspiracy.
To follow on from what friedo said, conspiracy generally requires the existence of an agreement between two parties to pursue an illegal action. Just giving a speech isn’t the same as having an agreement with someone.
As far as your hypothetical imam goes: it depends on where he is. In the U.S., he’s got First Amendment rights, and the general standard is that his speech is only illegal if his speech is likely to cause a crime imminently. Both likeliness and imminentness are required. The on-point Supreme Court case is Brandenburg v. Ohio.
I’m not as familiar with the situation in the UK, but it’s possible that an imam there could be charged with “encouraging or assisting crime”. Any UK Dopers want to weigh in on whether I’m reading this right, and/or whether there have been any cases like this?
When there is in fact a working and functional system of criminal justice (as opposed to gotcha prosecution), conspiracy generally requires, in addition to multiple people contemplating a scheme, some actual activity to advance the conspiracy, such as acquiring a weapon, or creating a reason for a proposed victim to be in a certain place at a certain time. I think the prosecution also has to show that the scheme was actually feasible, and did not require some improbable scenario like a cow falling from an airplane.
It would not be Conspiracy, for example, if I came on here and asked if anybody knew how to kill my mother in law and you responded “try poison”, unless I actually went out and bought poison, in which case you might wish to call an attorney and not answer any questions without him being present.
Yes, an udder flight of fantasy… 
Here is Ohio’s;
http://codes.ohio.gov/orc/2923
No.
In the US, here is a good example of such, similar in nature;
…Respondent, a data-entry employee in a county Constable’s office, was discharged for remarking to a coworker, after hearing of an attempt on the President’s life, “if they go for him again, I hope they get him…”
Of course this was a govt. employee, while still employed at will, they have a few extra protections non govt. employees do in the workplace.
I’m not sure about U.S. Law, but the UK law on conspiracy specifically says that you can still be guilty of conspiracy even if your plan couldn’t possibly work, so long as you believe it could (bolding mine):
[quote]
If a person agrees with any other person or persons that a course of conduct shall be pursued which, if the agreement is carried out in accordance with their intentions, either—[list=a][li] will necessarily amount to or involve the commission of any offence or offences by one or more of the parties to the agreement, or[*]would do so but for the existence of facts which render the commission of the offence or any of the offences impossible,[/list]he is guilty of conspiracy to commit the offence or offences in question.[/li][/quote]
I remember this point because it came into play in the “liquid-bombers” trial in the UK a few years back. Regardless of whether they could have successfully mixed the explosives in an airliner bathroom, they were still guilty of conspiracy to blow up the planes.
sigh moo-ving on…