We provide only information, not evidence. You're referring to tradecraft.
Suppose the police are investigating you, Matthew Dubé. If we check your Facebook page—because we're preparing a report about you—and you're sitting next to Jim Eglinski in one or two photos and there seems to be a link between you two, we could verify in our database whether you've ever transferred money to each other and establish whether you have financial ties.
We don't take everything available on Facebook. It must be linked to our database. If we want to establish links and identify members of your gang, we could certainly do so. However, it would need to be in our database as well so that we could share it with the police.