Imagine This:
An investigator finds a wallet at the crime scene. The wallet contains information apparently about its owner. But it also contains information about the investigator's family: home address, wife and children's names, schools they attend, place of business, etc.
What would the investigator conclude? First, that the wallet is a death threat made against his family. Second, the wallet was planted.
What that means is that the apparent owner named in the wallet is probably not the criminal in either the original crime or the death threat. After all, who would plant evidence against himself rather than someone else?
But then, suppose the criminal knows that the investigator would conclude thus. Therefore, he actually does plant his own wallet to deflect suspicion from him.
How likely would this be? In considering this likelihood, one must also consider that the number of other potential actors ranges from hundreds to millions. (Aside -- this is a probability problem known by mathematicians, although the criminal justice process appears to be unaware of the implications.)
Now imagine this scenerio. Someone sets bombs off in a major city. An unknown group, possibly called "The New European Al Qaeda" claims responsibility, in the process misquoting the Koran.
Now would a genuine group like that misquote the Koran, inadvertently? Very unlikely. That means that the claim of responsibility was bogus -- someone sent a false claim. That means we can rule out a radical fundamentalist Islam group as responsible for the bombings.
Or can we? Perhaps the radical group deliberately misquoted the Koran to throw suspicion off them and onto someone else.
What this means is that the authorities have to investigate carefully before laying blame for the bombings. The quote is a plant, and must not be taken at face value.