«I think most people aren’t aware of how much cheating goes on in marathons.» Were you aware? I wasn’t. But Derek Murphy, an independent marathon investigator, should know. He recently took particular care to examine the case of Jane Seo, a food and fitness writer in New York City. She finished second among the women in Sunday’s Fort Lauderdale Half Marathon in 1 hour and 21 minutes, a blazing 6:15 mile. But she cheated.