Among the questions we’re forced to wrap our heads around during “Amanda Knox” is why we’re watching it at all. Is it the allure of “true crime”? The allure of justice gone pear-shaped? The allure of Amanda Knox, the comely American who spent nearly four years in prison for the slaying of Meredith Kercher, her roommate in Perugia, Italy? Maybe it’s just a sordid fascination with the sordid—the “drug-fueled sex game gone wrong,” as the U.K. tabloids gleefully fantasized, all but ignoring the suspect actually convicted in Ms. Kercher’s 2007 murder.

Shouldn’t...