A woman who alleges Chicago police coerced her into falsely confessing to murdering her son may not call a physician to the stand to testify the boy’s death was accidental, a federal judge ruled Monday.In a written opinion, U.S. District Judge Amy St. Eve held Dr. Ryan Stevens is not qualified to offer an opinion about whether 4-year-old Jaquari Dancy’s death was an accident or homicide.The boy died in 2005 after he was strangled by an elastic band from a fitted bedsheet.His mother, Nicole Harris, spent nearly …