In Adams v. Speers, 473 F.3d 989 (2007), the Ninth Circuit held that CHP officer “off on a mission of his own creation, abandoning his assignment, picking up a buddy for no apparent reason except the excitement of the chase, barging in ahead of the police already engaged in pursuit, once attempting to use force against [decedent] and twice doing so, creating each time a serious hazard for himself as well as [decedent], and finally stepping out of his patrol car and, without warning and without the need to defend himself or the other officers, killing [decedent]”… …”not entitled to qualified immunity.” You can read the opinion here; the facts, which turned my stomach, show how cops can and do go overboard.