The dissenting opinion in the Wal-Mart sex-discrimination ruling presumes male managers are guilty of bias. And in the health care law, an assumption of guilt about people not paying medical bills lies behind the mandate to buy insurance. A presumption of innocence - that a person is blameless of wrongdoing unless proven guilty - is such bedrock of law that it is startling to see this civil right challenged in two recent court cases. One involves the US Supreme Court ruling on Monday that blocked a class-action suit against ...