Should NASA invest nearly a million dollars in an obscure Russian scientist's antigravity machine (it has failed every test and would violate the most fundamental laws of nature)? Should the Patent and Trademark Office have issued Patent 6,362,718 for a physically impossible motionless electromagnetic generator (which is supposed to snatch free energy from a vacuum)?

There is, alas, no scientific claim so preposterous that a scientist cannot be found to vouch for it. And many such claims end up in a court of law after they have cost some gullible person or corporation a lot of money. How are juries to evaluate them?

How can you recognize questionable scientific claims? What are the warning signs of fraud? Here are seven indicators that a scientific claim lies well outside the bounds of rational scientific discourse. Of course, they are only warning signs -- even a claim with several of the signs could be legitimate.