Federal investigators are focused on one Ferguson, Mo., police officer who fatally shot an unarmed black teenager, but at least five other police officers and one former officer in the towns 53-member department have been named in civil rights lawsuits alleging the use of excessive force. In four federal lawsuits, including one that is on appeal, and more than a half-dozen investigations over the past decade, colleagues of Darren Wilsons have separately contested a variety of allegations, including killing a mentally ill man with a Taser, pistol-whipping a child, choking and hog-tying a child and beating a man who was...