When forming a plan to commit a major crime it makes sense to limit the number of people required. That number could range from two individuals to dozens if not hundreds of people. The more people involved the greater the risk that loose lips could see the plan either fail in the lead up or fail in the execution. Even if the plan is successful there's a risk that those involved will be exposed in the subsequent investigation or through loose lips or a conspirator coming forward with evidence of their involvement and naming names.
An unwitting participant (someone who had a small but important part to play) could come forward once they realise that without their actions the crime could not have been carried out.
If you do have a preferred conspiracy it would be interesting to hear how many people (minimum) would be required either directly and/or indirectly in the execution and aftermath.
What?s the MINIMUM number of people required for your CT to work?