Jeff sez, "Researchers often use Photoshop to clean up the images they produce in the laboratory. If the experiment didn't go quite right, a bit of tampering can make a gel look like things did work. Editors at Science, Nature, and other journals are turning into detectives, using new tools to hunt for fraudulent images."

And the level of tampering they find is alarming. "The magnitude of the fraud is phenomenal," says Hany Farid, a computer-science professor at Dartmouth College who has been working with journal editors to help them detect image manipulation. Doctored images are troubling because they can mislead scientists and even derail a search for the causes and cures of disease.

Ten to 20 of the articles accepted by The Journal of Clinical Investigation each year show some evidence of tampering, and about five to 10 of those papers warrant a thorough investigation, says Ms. Neill. (The journal publishes about 300 to 350 articles per year.)