What is a group of crows called?

The most widely used term is "murder." A group of crows can also be called a flock, muster or storytelling of crows.

This is based on the (fallacious) folk tale that crows form tribunals to judge and punish the bad behavior of a member of the flock. If the verdict goes against the defendant, that bird is killed (murdered) by the flock. The basis in fact is probably that occasionally crows will kill a dying crow who doesn't belong in their territory or much more commonly feed on carcasses of dead crows. Also, both crows and ravens are associated with battlefields, medieval hospitals, execution sites and cemeteries (because they scavenged on human remains). In England, a tombstone is sometimes called a ravenstone.

The poetic term used in literature is a "murder." Scientists would call them a flock. A murder of crows.

The poetic term used in literature is a "murder." Scientists would call them a flock.