As General Motors is scheduled later this year to face yet another bellwether trial over allegations it covered up a deadly ignition switch flaw, it can take some comfort from its generally-successful trial record. But critics of the bellwether system are saying that way of lining up trials does not provide an accurate way of keeping score.

Last month, the seventh bellwether trial, held before New York Southern District Judge Jesse Furman, ended in a third jury verdict in GM’s favor.